Isaac

D&D is the definitely the best known TTRPG, to the point that it is almost ubiquitous with TTPRGs as a whole. There are a lot of rules and mechanics available to give structure to anything you might want, while being flexible enough to not have to use any of it. Because it is so big, there are plenty of resources, communities, and books available for D&D. It is a great place to start to get familiar with the hobby, even if it can be a steep learning curve at first.