A Federation fleet in 2374.
Fleet is a word often used to describe a group of starships or other vessels working or travelling together. Though they are often used in war, fleets can be used for peace. Throughout history fleets have been prevalent in space as well as on planets.
Fleets on Earth
In the history of Earth fleets have been used for many purposes, such as war. Since these conflicts took place on a planet, they involved naval ships as opposed to starships.
Fleets in Space
Throughout the history of Starfleet and beforehand, fleets have existed in space as well. However some instance are more striking than others. There are many times when the Federation has amassed large fleets for the defense of their territory, or other races. Federation fleets have been used in
Voyager encounters a fleet of Borg Cubes.
battles such as Wolf 359, the Battle of Sector 001, the Dominion War, and many others. Other species fleets have been seen as well, the Borg and Species 8472 fought against each other using fleets in 2373. (VOY: "Scorpion", "Scorpion, Part II")
Other Uses
Offense is not the only use for fleets however. In 2368 Geordi La Forge derived a tachyon detection grid for the purpose of detecting cloaked Romulan ships during the Klingon Civil War. Multiple Federation starships were required to create the grid. (TNG: "Redemption, Part II")