Dungeons & Dragons (dnd, d&d for short) is a tabletop fantasy roleplaying game first published in 1974 by Gary Gygax and David Arneson and has carried itself from then all the way until nowadays in 2021 where 5th edition is now a thing.
Pathfinder is often considered D&D 3.75e, as it was created with the OGL in 2001.