📄️ Polkadot Wiki
The Polkadot Wiki is a great starting point and source of knowledge in terms of basic concepts and introductions into advanced concepts. The tools section offers an additional rich pool of tools that you might find useful.
📄️ Polkadot 1.0
The blog post "Polkadot v1.0: Sharding and Economic Security" is a great introductory blog post that goes deep into how Polkadot approaches sharding, finality, backing, approval checking, data availability, approval checking, and disputes.
📄️ Polkadot Protocol Specification
The Polkadot Protocol Specification describes the Polkadot Host and Polkadot Runtime. It is the shared implementation of the Rust, Go, and C++ implementations that are also referenced here.
📄️ Web3 Foundation Research
The Web3 Research Wiki hosts original research and provides insides into the more advanced concepts of Polkadot. It covers topics such as protocols, economics, security, and cryptography.
📄️ Polkadot Support
Polkadot Support is a knowledge base that answers general questions about Polkadot.
📄️ Substrate Docs
The Substrate documentation covers concepts, tutorials, and a reference on Substrate.
📄️ polkadot.study
Educational hub for developers by developers
📄️ PBA Book
The Polkadot Blockchain Academy course materials have been published as free learning material: