The Fast Track Server is a shared server for players up to Level 55. XP is increased for mob kills, but not for quest rewards. As well, Essencetapping and Aethertapping XP is double, so this is a good way to increase those levels. There are some areas of Atreia where there is no Fast Track Server Option.
To access the fast track server there are two options. Select <Menu>. then <Go to Channel>, and then <Go to Fast-Track Server >. Or click the fast track icon above the experience bar at the bottom of the UI.
Once clicked, a box will open up giving the choice of Standard Server or Fast Track Server. If the fast track option is grayed out, the area does not support that server. Chose the server, and click <Move> to change servers.