Frigates are fast, but weak. Good for hit and run tactics.
Destroyers are slightly slower, but normally pack more firepower and health.
Cruisers are slow, but kinda tanky. Can take a moderate amount of hits.
Battleships are very slow, but have a lot of damage output and health. Great for frontline and backline assault. Can be decent drone carriers.
Capital ships are big and bulky, with the firepower, damage output, and health to match. Very slow.