Your starting class in Baldur's Gate 3 determines your ability scores and what abilities your character will start the game off with. Each class can be fully leveled throughout 12 levels to reach its maximum potential, but all 12 levels don't need to be placed into only one class.
Baldur’s Gate 3: How To Multiclass
The class you start as won’t be the only class you’re stuck without throughout your playthrough of Baldur’s Gate 3; here’s how to multiclass.