All this data is potentially out of date, and should be taken with a truckload of salt
Covert Ops ships (also known as covops) are tech II frigates that are built around stealth and unseen observation.
Covert Ops ships are one out of two frigate class hull - the other being Stealth Bombers - that can use a Covops Cloak, and are thus able to warp while cloaked. They also receive a bonus to the scan time of both recon and scan probes, making them adept at quickly locating safespotted targets, as well as scanning down exploration sites.
The fact that they can move at fairly high subwarp speed while cloaked, along with the fact that they can warp while cloaked, makes Covert Ops vessels very useful for scouting and running small, valuable cargos through dangerous lowsec or 0.0 regions. Covert Ops ships are one of the very few ship classes that can jump into a 0.0 bubble camp and have a good chance of escaping.