General layout of a Man-of-War
The Man-O-War is a naval ship that was designed for combat and not for merchant service. It was typically heavily armed and pirates avoided them. Of course sometimes such ship were used to transport treasure or acted as escort to merchant ships.
Man-O-War Ship. Click here to enlarge.
Also the ships would be deployed strategically just beyond the horizon or in the shadow of merchant ships as a trap for would be pirates. While most pirates avoided tangling with men-o-wars, Bartholomew Roberts was known for not making such a fine distinction and would often tangle which such ships if he knew they were carrying a substantial prize.
There are three general classes of Man-O-Wars.
Ship of the Line
Ship of the Line
The Ship of the Line is the main battle ship of a Navy and the largest of the Man-O-Wars. It was ship rigged with three masts. Its guns were arranged on three gun decks.
Depending on the time period Ships of the line carried between 32 and 144 guns arranged on three and sometimes four decks. This is because they continued to get larger from the 16th to 18th century. By the mid-18th century the typical ship of the line had 74 guns on three decks.
Sometimes a smaller Ship of the line would have its guns on just two gun decks instead of the more traditional three. Typically the cannons were around 32 to 42 pounders. The Galleon, for all practical purposes is also a Man-O-War and was Spain's Ship of the Line.
The Frigate was the midsized Man-O-War, It was still ship rigged with three masts but was noticeably smaller than a Ship of the Line. It would typically have a full battery of guns on the gun deck and a light battery on a spar deck.
Typically the Frigate would carry between 24 and 40 guns ranging in size between 12 and 24 pounders. One of the few surviving Frigates is the USS Constitution.
A small sailing-vessel resembling a brig, carrying a main and fore mast and a supplementary trysail mast close behind the mainmast; employed as a warship. The snow was the smallest of the warships. It was a common warship used in the American Colonies and the Caribbean.
See Corvette, below by comparison.
Corvette (Sloop of War)
The Corvette was a speciallized "brig rigged" sloop of war with only two masts. A sloop of war was a two or three masted fore and aft rigged ship with a single fighting deck.
The Corvette also has her guns arranged on a single fighting deck.
Two masted sloops of war and corvettes typically carried between 12 to 20 guns ranging between 6 to 12 pounders. Larger three masted sloops of war could carry more guns but would still have a single fighting deck
As the ships become less well armored its ability to maneuver increases. So this would make the both Corvette and sloop-o-war a fast light ship that could attack quickly but not bring an enormous amount of fire power to hand.