In layman’s terms from Google AI: A cab capture and an IR are not the same thing, though they are related. A cab capture is a specific type of IR, but not all IRs are cab captures. IRs (Impulse Responses) are essentially audio files that record the way a system, like a speaker cabinet, reacts to a signal, while a cab capture specifically focuses on capturing the unique sound of a particular cabinet and microphone setup.
Search for cab capture here in the forum and you should find an existing thread with a link to a YouTube video comparing the two etc.
Edit: found it 