SMART capable HDDs do (S)elf (M)onitoring and (A)nalysis, and have a (R)eport (T)echnology too 🙂
So the drive keeps an eye on whether certain things are off, like read signal quality from the heads, spin-up time, seek times, track positioning accuracy, whatever internal ... and gives a report when asked. You can enable BIOS to ask for a report during system POST, right after detecting the drive.
The idea is to give an early warning about a HDD that is about to fail but hasn't yet, for a more seamless exchange procedure.
regards, Peter