Balamb Garden is a mercenary training center, preparing young soldiers and students to become members of SeeD, a peacekeeping force-for-hire. Four of the main characters in Final Fantasy VIII (Squall, Quistis, Zell, and Seifer) are from Balamb Garden. Within the Garden is everything a student needs to succeed; classrooms, dormitories, an infirmary; even a training center filled with live creatures (that players can visit to earn experience points).
On Final Fantasy VIII's second (of four) discs, it is revealed that Balamb Garden is actually a mobile structure, and the player spends a large portion of the game flying Garden around the world map to reach previously unreachable locations.
There are several competing Garden structures that are housed in different nations. Galbadia Garden is the main enemy of Balamb, although one of your party members (Irvine) is recruited from it. The smaller Trabia garden, located in a snowy mountain pass, was home to Selphie (another main character in Final Fantasy VIII) but gets destroyed by a Galbadian missile launch toward the end of Disc Two.