Consent evidence typically includes the timestamp, source (which form or flow), IP address, and confirmation method (single or double opt-in) for a given subscriber. It exists to answer, on demand, "can you show this person actually agreed to this?"
This is distinct from suppression-list membership, which reflects the current state of whether someone should be mailed; consent evidence is a historical record of how that state came to be, retained even after someone unsubscribes.
PulsePigeon's consent-evidence handling is documented on the consent-policy page, covering what's captured, how long it's retained, and how it factors into marketing-send eligibility.