Baldur's Gate 3 is built on the Dungeons & Dragons Fifth Edition system, adapted for CRPG by Belgium-based developers Larian Studios. As with any tabletop-to-video game adaption, Larian has had to add, remove, and tweak the Fifth Edition rules to fit Baldur's Gate 3.
Tabletop players will easily recognize the familiar races, classes, features, and monsters in Baldur's Gate 3. However, it's worth noting the more major changes that Baldur's Gate 3 makes to Fifth Edition, so that players who are relying on their tabletop knowledge don't find themselves missing out.