> For the complete documentation index, see [llms.txt](https://docs.quarkchain.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.quarkchain.io/core-concepts.md).

# Core Concepts

- [Soul Gas Token](https://docs.quarkchain.io/core-concepts/soul-gas-token.md)
- [Inbox Contract](https://docs.quarkchain.io/core-concepts/inbox-contract.md)
- [L2 Blob](https://docs.quarkchain.io/core-concepts/l2-blob.md)
- [web3://](https://docs.quarkchain.io/core-concepts/web3url.md)
- [L1 Header Hash History](https://docs.quarkchain.io/core-concepts/l1_header_hash_history.md)