CVL are light carriers or seaplane tenders? I'm still getting used to some of the other classifications.
DD = Destroyer
CL = Light Cruiser
CLT = Torpedo Cruiser
CA = Heavy Cruiser
CAV = Aviation Cruiser
AV = Seaplane Tender
CVL = Light Aircraft Carrier
CV = Standard Aircraft Carrier
BB = Battleship (slow)
FBB = Battleship (fast, Kongou class)
BBV = Aviation Battleship
SS = Submarine
SSV = Sub that can carry airplanes (specific name?)
There are others, but the ones I listed are the most common I think. Most of the others only have 1 or 2 units in them, so it's easier to just refer to them by the unit name.
Blogged the post so that I can look into the classifications whenever I need them.