Quote Originally Posted by andrewt
Isn't almost everything "light" in this time period? Not an expert, but from what I understand, cav only wore armor as parade dress. They ditched the armor when actually fighting.
Quite a few heavy cavalry used breastplates (cuirassiers). Heavy cavalry tended to ride heavier mounts and be reserved for shock action. Light cavalry would do more scouting and screening.

Light infantry were specialised more for skirmishing - either a company in a battalion or entire regiments.

I don't think the functional differences were as pronounced as the nomenclature however. In a pitched battle, light cavalry would be expected to perform charges. And line infantry would sometimes fight in loose order.