The shuttlebay (also called a hanger deck or launch bay) is an area on a starship or space station where shuttlecraft can be stored and maintained for operations off the vessel or station.
When not launching or receiving craft the space doors for a shuttlebay are usually closed. When they are opened a force field is deployed over the opening, which can be penetrated by shuttles as the launch and are recovered without compromising the atmosphere within the bay itself.
Shuttlebays were often equipped with tractor beam emitters to assist in the landing of damaged or inoperable vessels. (TNG: "Time Squared")