Info: BTC Parachain Roles
Vaults:
Collateralized intermediaries who hold BTC locked on Bitcoin. Any user can become a Vault by simply locking DOT collateral. The only requirements are (1) a Bitcoin wallet, (2) a Polkadot wallet and (3) some DOTs.
Staked Relayers;
Make sure the BTC Parachain is up to date with the state of Bitcoin by submitting block headers to BTC-Relay, the Parachain’s Bitcoin SPV client. Staked Relayers also flag (potentially) invalid blocks. Requirements: (1) Bitcoin full node, (2) Polkadot wallet, (3) some DOTs.
Parachain Validators:
Participate in the BTC Parachain’s DPoS consensus, as per Polkadot consensus rules. Requirement: (1) Parachain full node and (2) DOTs.