Polkadot SDK

The foundational framework for building custom, application-specific blockchains called parachains. It provides a modular library of pallets (runtime modules) for core functionalities like staking, governance, and smart contracts, allowing developers to compose their chain's logic without writing everything from scratch. Substrate chains can run solo or connect to Polkadot.

The relay chain is the central, coordinating blockchain of the Polkadot network. Its primary functions are:

• Shared Security: Providing pooled security from its validator set to all connected parachains.
• Interoperability: Enabling cross-chain message passing (XCMP) between parachains.
• Governance: Managing network upgrades and treasury via an on-chain governance system. It does not support application logic itself.

A collection of tools that allows a Substrate-built blockchain to easily connect to the Polkadot or Kusama relay chain as a parachain or parathread. It handles the compatibility layer, including:

• Collator Nodes: Nodes that produce proof-of-validity blocks for the relay chain validators.
• Embedding the necessary logic for cross-chain messaging and adhering to the relay chain's consensus.

The core runtime development framework within Substrate. It is a library of pallets and supporting libraries that simplify building a blockchain's state transition function. Developers use FRAME to:

• Select and configure pre-built pallets (e.g., pallet_balances, pallet_sudo).
• Create custom pallets for unique business logic.
• Define the entire runtime as an aggregation of these interoperable modules.

The standard messaging format for communication between parachains, and between parachains and the relay chain. It is not a specific protocol but a format that defines how messages are structured and interpreted, enabling:

• Asset transfers across chains.
• Remote function calls (cross-chain smart contract execution).
• Governance across the ecosystem. XCMP is the transport protocol that carries XCM messages.

A cold wallet application for key management, allowing users to store their private keys on an air-gapped mobile device. It signs transactions offline via QR codes, providing a high-security alternative to hot wallets. It is a critical tool for governance participants and validators who need to sign transactions without exposing keys to an internet-connected device.

The foundational layer of the SDK, Substrate is a modular, open-source framework for building custom blockchains. It provides core components like a p2p networking layer, consensus algorithms, and a WebAssembly (Wasm) runtime environment. Developers can use pre-built pallets (runtime modules) for common functionalities like staking, governance, and smart contracts, or create their own.

Cumulus is a collection of tools for building parachains that connect to the Polkadot or Kusama Relay Chain. It handles the complex networking and consensus integration, allowing developers to focus on their chain's business logic. Key components include:

• Collator Nodes: Nodes that produce parachain blocks for validators on the Relay Chain.
• Embedded Consensus: Integrates the Relay Chain's consensus (BABE/GRANDPA) into the parachain.
• XCMP Support: Built-in functionality for cross-chain messaging.

Parachains are sovereign, application-specific blockchains that connect to the Polkadot or Kusama Relay Chain for shared security and interoperability. They are the primary way to build and deploy a blockchain using the Polkadot SDK. Key examples include:

• Acala: A DeFi hub offering a stablecoin (aUSD) and a decentralized exchange.
• Moonbeam: An Ethereum-compatible parachain for easy porting of Solidity dApps.
• Astar Network: A multi-chain smart contract platform supporting WASM and EVM.

The Relay Chain is the central chain of the Polkadot network, co-created using the Polkadot SDK. It is responsible for network security, consensus, and cross-chain interoperability. The SDK enables the creation of two canonical relay chains:

• Polkadot: The production network focused on stability and high-value applications.
• Kusama: The "canary network," a faster, more experimental environment for rapid innovation and testing before deployment on Polkadot.

Parathreads offer a flexible, block-by-block connection model for blockchains that don't need continuous parachain slot access. Built with the Polkadot SDK, they allow projects to pay for security and messaging only when they produce a block. This is ideal for:

• Low-throughput applications that don't justify a full parachain lease.
• Bootstrapping projects testing economic viability.
• Fallback option for parachains that lose their slot auction.

The Polkadot and Kusama Treasuries, governed by their respective token holders, are a major source of funding for ecosystem development. Hundreds of proposals have been funded to build tools, applications, and research using the Polkadot SDK. This funds:

• Development of core infrastructure like wallets, explorers, and indexers.
• Marketing, education, and community events.
• Research initiatives for scaling, cryptography, and new pallets.

Substrate is the foundational Rust-based framework within the Polkadot SDK for building customizable, production-ready blockchains (called parachains or solo chains). It provides core modules like consensus, networking, and a modular runtime, allowing developers to focus on application logic. Key features include:

• FRAME (Framework for Runtime Aggregation of Modularized Entities): A pallet-based system for composing runtime logic.
• Forkless Runtime Upgrades: Enables on-chain governance to upgrade the blockchain without a hard fork.
• Built-in Interoperability: Designed to connect to the Polkadot or Kusama relay chains.

Polkadot-JS is the primary JavaScript toolkit for interacting with any Substrate-based blockchain, including Polkadot, Kusama, and their parachains. It consists of:

• Polkadot-JS API: A promise-based interface for querying chain state, submitting transactions, and listening for events.
• Polkadot-JS Apps: A versatile, extensible web application that functions as a wallet, block explorer, and governance dashboard.
• Polkadot-JS Extension: A browser wallet extension for managing accounts and signing transactions. It is the ecosystem's standard for front-end development and user interaction.

XCM is a messaging format and language standard within the Polkadot SDK that enables communication and value transfer between different consensus systems (parachains, parathreads, and external networks via bridges). It is not a transport protocol but a format for expressing intent. Key concepts include:

• Vertical Message Passing (VMP): Communication between a parachain and the relay chain.
• Horizontal Message Passing (HRMP/XCMP): Direct parachain-to-parachain messaging (XCMP is the transport layer for XCM).
• Multi-Asset & Multi-Location: Can represent and transfer any asset to any location in the consensus universe.

Cumulus is a set of tools within the Polkadot SDK that simplifies connecting a Substrate-built blockchain to the Polkadot or Kusama network as a parachain or parathread. It handles the complex networking and consensus requirements for shared security.

• Cumulus Consensus: A consensus engine that follows the relay chain, allowing the parachain to focus on its state transitions.
• Collator Nodes: Nodes that produce parachain block candidates for relay chain validators.
• Rococo & Westend: The primary testnet environments for parachain deployment and XCM testing before launching on mainnet.

The Relay Chain is the central, coordinating blockchain of the Polkadot and Kusama networks. Built with Substrate, its primary functions are:

• Shared Security: Provides consensus and finality for all connected parachains via its nominated proof-of-stake (NPoS) validator set.
• Interoperability Hub: Facilitates trust-free messaging and asset transfers between parachains via XCM.
• Governance: Hosts the on-chain governance system that controls the network's treasury and upgrade processes. Parachains lease slots on the relay chain via a candle auction mechanism.

Parity Signer is a secure, air-gapped mobile application for managing cryptographic keys and signing transactions for Polkadot and Substrate-based chains. It enhances security by:

• Cold Storage: Private keys are generated and stored exclusively on an offline mobile device.
• QR Code Transactions: Transactions are signed offline via QR codes, preventing exposure to internet-connected devices.
• Multi-Chain & Multi-Account Support: Manages accounts for numerous networks from a single, secure vault. It is a critical tool for high-value accounts like validator operators and governance participants.