A Virtual Tabletop, developed by SmiteWorks USA LLC, for a huge amount of game systems, with a metric fckton of (official!) content available in either their store or even on Steam.
Once you get familiar with the way FG does things and maybe get over the opinionated UI, it’s very versatile and powerful both in automation and manual intervention.
I found it to be maybe a bit lacking in final polish and ease of preperation, when compared to Foundry VTT, but what it lacks it more than makes up in the ability to spontaneously correct something, intervene or even make up on the spot. The draggable dice (or better draggable everything) is always a player favorite, together with easy on-the-fly automation using (pretty easy to learn) effect syntax in the combat tracker for the Game Master!
I also made a quick overview of what to do to get up and running: Fantasy Grounds - ELI5