Hey, generally frigates were the fast larger three masted ships. Sloops were more often smaller two masted ships with less draft (the distance the hull of the ship goes below the waterline. Sloops were mostly employed patroling the intercoastal waterways, while frigates ran blockaide duty.
The ships were also ranks by the number of guns they carried. Gunships were usually even smaller vessels that did not "go to sea".

And, Hey, I'm new to the board and just want to say it's great!