What does checking hashes of documents mean? Isn’t stuff either encrypted or not? This might not be a good look for me to be confused by this as a web dev/prog

What does checking hashes of documents mean? Isn’t stuff either encrypted or not? This might not be a good look for me to be confused by this as a web dev/programmer, but I does that mean they are securely or otherwise hashing everything they store on all users? Drive, Gmail and other Google services have tons of data. After THats they are also still only checking hashes?