FF Advance Server is a platform provided by Garena to only a few of the Free Fire players and these players can play and experience the upcoming features of the game before other Free Fire players can. How exciting is that! However, not all gamers are lucky enough to participate in this Advance Server.
This is basically a testing platform introduced by the makers as they can get to know about the feedback of the game features before they are released to the public. Not only this, Garena can know about the bugs and any possible lags through this server. This way they can improve the game from all aspects before generally releasing the update.