The Geats were a North Germanic tribe from southern Sweden. They are sometimes called Goths. The Old English word Geatas and the old Germanic word Goth are said to both derive from the meaning "to pour" and this probably has something to do with rivers and water transport in the area of southern Sweden. At the time of the events in Beowulf, the Geats were relatively independent from other Swedes as a unified nation, although to what extent is a matter of debate. Note that "Germanic" refers to a number of different Northern European cultures which are close geographically and share a common Proto-Germanic (parent) language. For instance, Danish, Swedish, Norwegian, German, and English all derive from this parent language.
Beowulf himself was a Geat. In the section discussing how Beowulf comes to Heorot, the narrator talks of a "thane of Hygelac." Hygelac was king of the Geats when Beowulf was a young man. Hrothgar and his people are known as the Scyldings, a Danish tribe. When Beowulf and his men arrive on the Scyldings' shore, he says, "We are men of the Geatish nation and Hygelac's hearth-companions. My father was well-known among the tribes, a noble leader named Ecgtheow." Beowulf would have sailed from southern Sweden to the Danish island of Zealand through one of the straits connecting the North Sea and the Baltic Sea.