In dance music, the breakdown removes the kick and lets pads, vocals or melody breathe. In metal and hardcore, a breakdown is the opposite: a slow, heavy, rhythmic section. In funk, breakdowns strip the band to bass and drums.
Whatever the genre, breakdowns create the contrast that makes the next section hit harder.
Using it in a prompt
Specify what remains in the breakdown ("breakdown with only piano and pads") so the generator knows what to strip back.