Star Trek 101: What is Starfleet?

Starfleet, a military but not militaristic space armada in the Star Trek universe, serves as the scientific, diplomatic, space exploration and defense organization of the United Federation of Planets.

Individuals representing more than 150 species belong to Starfleet or attend Starfleet Academy; Earth citizenship is not a requirement.

The term Starfleet is used commonly from the "Court Martial" episode of the Star Trek original series onward, but not before a string of experimental terms had been employed, such as Star Service, Spacefleet Command and United Earth Space Probe Agency. UESPA references occur in episodes of Star Trek: Voyager and Star Trek: Enterprise, and in the movie Star Trek: Generations.

In Star Trek: Enterprise a version of Starfleet is shown to have been in existence on Earth at least 18 years before the founding of the Federation, with officers having completed "Starfleet training".

Starfleet famously follows a Prime Directive of non-interference, deriving originally from Vulcan policy. Vulcans historically used the development of warp engines as a litmus test for a species to be ready for first contact, and the principle became a part of the charter of the United Federation of Planets and therefore a standard operating procedure for Starfleet.

Starfleet headquarters are located in the Fort Baker area of San Francisco near the Golden Gate Bridge, with officer training facility Starfleet Academy located nearby in the Presidio.

Starfleet's mission is largely exploratory, with the search for unknown sentient life its primary focus. Ship's weapons were originally intended for defense only, until the retrofitting of the Enterprise NX-01 in Star Trek: Enterprise following the Xindi attack on Earth in 2153.

Branches of Starfleet include the Starfleet Judge Advocate General (JAG), which oversees legal matters within Starfleet, and the Starfleet Corps of Engineers, which has been the subject of a series of ebooks from Pocket Books. Starfleet also has medical, security, operations and tactical branches.

Ranks within Starfleet are similar to those in the United States Navy and the British Royal Navy. Flag officer ranks in descending order are: Fleet Admiral, Admiral, Vice Admiral, Rear Admiral, Commodore/Rear Admiral. Although the Enterprise is usually considered Starfleet's flagship, it is not commanded by a flag officer. Field command officers in descending order are: Captain, Commander, Lieutenant Commander, Lieutenant, Lieutenant junior grade and Ensign. Starfleet Academy graduates are commissioned at the rank of Ensign, with the exception of medical graduates who are commissioned as Lieutenant junior grade.

Most of the regular cast of all of the Star Trek television series and featured characters in movies are commissioned officers, with the exception of Chief Petty Officer Miles O'Brien in Star Trek: The Next Generation and Deep Space Nine. The most junior enlisted rank is crewman.

Honolulu Exopolitics Examiner Michael Salla, Ph.D. reports on Examiner.com that the Exopolitics Institute in Hawaii offers a certificate in extraterrestrial diplomacy, presumably in anticipation of real-life Starfleet diplomatic training.

http://www.examiner.com/x-11230-Star-Trek-Examiner~y2009m8d17-Star-Trek-101-What-is-Starfleet