Cruisers are by far the most numerous and varied craft in most space navies, and come in many sizes and varieties including  Heavy, Command,  Medium, Supplemental,  Light, Research and Medical Cruiser types amongst others. One of the oldest designations, the term Cruiser refers to a large array of vessel types and sizes. Cruisers can be both general purpose and mission specific, with many capable of autonomously switching between the two extremes when needed. Cruisers are not as large or powerful as Battleships or Dreadnoughts, but can often be as effective in military conflict. Cruiser are also highly varied in their abilities to explore and expand the boundaries of established governments. First contacts, stellar and planetary research as well as diplomatic negotiations are all well within the purveyance of Cruiser class vessels. Cruisers can also easily switch to medical emergency mode, search and rescue and evacuation when needed. Most cruisers have a large science base, consisting of numerous sensor system, independent science labs and numerous on-board departments that specialize in a wide variety of space and planetary science. 

Cruisers often have a large engineering contingent, giving a cruiser unique forward capabilities while in deep space. Cruisers can maintain lengthy patrols and explore well beyond the boundaries of established boarder space. Cruisers are often well armed and very capable of defence and combat when necessary. Cruisers are the mainstay of the Romulan Navy, and an expansive part of the Federation and Klingon Navies.

Command Cruisers are designed to operate as mobile star-bases and tactical operations focal points during both emergency situations and times of conflict. Command Cruisers act as a Flagship for medium to large fleets, often superceding command of Battleships or Dreadnought. Command Cruisers can coordinate the operations of nearly 100 or more other vessels, having specialized on-board Command-and-Control systems, tactical data systems, and on-board analysis systems that allow a front line commander to quickly assess the changing political and military situation for dozen of parsecs. 

Command Cruisers are able to coordinate large scale research operations, but have only a moderate research ability themselves. Most Command Cruisers are equal or larger than Heavy Cruisers, and have firepower equivalent to most Dreadnoughts. Command Cruisers do have a much shorter range, owing to the large number of extra crew members on-board, which often include Intelligence operatives, special forces personnel, Military strategists, tactical engineering/analysis personnel and other specialized military or research personnel. 

Command Cruisers also have surprisingly extensive repair and medical systems, allowing them to act as a rescue vessels when necessary.