Delegators hold the logic to delegate voting or proposition power for a given type of governance token. There is 4 different Delegators that PalPools can clone to create PalLoans :

Basic Delegator

Based on Governor Alpha/Bravo governance, and on COMP-like tokens.
Currently used for COMP & UNI PalPools.

Aave Delegator

Based on Aave Governance, and the AAVE token delegation logic.
Currently used by the AAVE PalPool.

Aave Claimer Delegator

Also Based on the Aave Governance, and inheriting the delegation logic from the Aave Delegator, this Delegator adds Claim logic to retrieve any rewards earned by stkAAVE tokens during the delegation period.
Currently used by the stkAAVE PalPool.

Snapshot Delegator

Based on the Delegation Strategy that can be applied in a Snapshot space, and that uses the Gnosis Delegate Registry (0x469788fE6E9E9681C6ebF3bF78e7Fd26Fc015446).
Currently not used by any PalPool.