Special Operations Division
Captain is a senior Line Officer rank, it's insignia is four solid pips. It ranks above Commander and below Commodore. The most prominent billet for a Captain is as the Commanding Officer of a starship, normally medium to larger vessels. Captains also command Starbases or planetary bases, minor Sectors, and similar postings. Outside of Command, Captains serve in a range of Staff postings, Operations Division Captain's may oversee construction at shipyards, or departments on large bases. The Marine Corps equivalent is Colonel.
As a position the Commanding Officer of a ship is called Captain, regardless of rank, further more Captain (Marine) may be referred to as Major as there "there can only be one Captain" and as a courtesy they are elevated to the next rank.