An away team is a team of specialized personnel from a Starfleet starship or starbase that are assembled to perform a mission on a planet's surface or aboard another starship. Starfleet captains are generally prohibited from leading away missions (unless circumstances dictate their presence), and away missions are usually led by the first officer.
The term away team has been used since the 22nd century, but during the 23rd century away teams were often referred to as landing parties or boarding parties. (Star Trek: Enterprise; Star Trek: The Next Generation)
A new type of away team was developed aboard the stranded starship USS Voyager, a concept of an elite hazard team ready to respond to dangerous situations that a typical away team might not be prepared for. The USS Voyager Hazard Team concept was later adopted aboard other vessels after Voyager returned to the Federation, and many members of the hazard team of Voyager became part of the USS Enterprise-E Hazard Team. (VOY video game: Elite Force; TNG video game: Elite Force II)