VCT is the name of the record. VC is what it carries. The payload is the signed statement defined by the vc entry on this site — issuer, subject, and claims — not a second meaning of the word VC.
The project decides the policy around the VCT: transferable or not, vested or not, what the claims stand for. That policy sits on the envelope. The payload remains a VC.
DID identifies the subject. A VCT records what a project has recognized, using a VC as payload. ABT is the settlement asset.