# Core Concepts

- [Permissionless Pools](/core-concepts/permissionless-pools.md): Liquidity providers are integral to any DeFi protocol, and Spectra is no different.
- [Principal & Yield Token](/core-concepts/principal-and-yield-token.md): Principal Tokens (PTs) and Yield Tokens (YTs) are the core primitives and components of the Spectra protocol, also called as yield derivatives.