Fantasy Grounds is an application acting as a virtual online gaming table primarily intended for pen and paper style narrative role playing games.
Fantasy Grounds is designed to perform many of the things you can do while playing at a conventional gaming table and move it online.
Run games as the gamemaster or take part as a player, the application provides all the necessary tools to communicate, manage information and perform tasks such as rolling the dice or creating drawings.
Fantasy Grounds is not a roleplaying game and it is definitely not a computer roleplaying game, as you can't really play it on your own.
Fantasy Grounds is a set of tools to provide the means for you and your friends to play your pen and paper roleplaying game online. (Quoted from the FG website)