1797 The Constitution, a forty-four-gun US Navy frigate built to fight Barbary pirates off the coast of Tripoli, was launched in Boston Harbour.

So I wanted to know, what is a frigate?

Historical
Frigates were originally light, fast warships with oars and sails that originated in the Mediterranean in the late 15th century. They were the backbone of the early American Navy and were used to protect merchant ships, capture enemy cargo, and fight battles.
Modern
A frigate is a modern warship that is smaller than a destroyer and is typically armed with a single main gun, anti-aircraft guns, and anti-ship missiles. Frigates are used for a variety of purposes, including defending national waters, patrolling coastal areas, supporting ground troops, and projecting power across the oceans.
The term "frigate" comes from the Italian word fregata.