The overflow is Guild Wars 2's version of a queuing system.
 The basics
The overflow version of a map acts exactly like the normal version except that it is universal to all worlds on a continental server (EU and US are separated), meaning that players from other full worlds may also be present. While World versus World can be joined from the overflow, you cannot see any information about worlds or their scores. The maps will show up as "Unknown Borderlands", but positionally, the Unknown Borderlands will lead you to the Borderlands it would normally show in that position. The name of the Eternal Battlegrounds remains the same. Also note that on the overflows, World versus World bonuses are not applied.
If the destination is very popular, the game might have multiple overflows. You will not necessarily transfer to the same overflow as others, unless they are members of your party (or squad [verification requested]) and travel at the same time. If you are not in the same overflow as your party member(s), you can right-click their party icon and click the join button. Tho if the map is full this option will not be listed.
 Leaving the overflow
When a spot becomes available to you in your world's normal zone, you will be given the option to enter that zone, reenter the queue, or leave the queue altogether to continue playing in the overflow. When a party has multiple members in an overflow, the queue will only prompt the individual members to travel if the main world has room for all of the present party members. The choice to travel does not necessarily have to be universal for these party members. Once you've left the queue, the only way to be queued again is to reenter the zone completely, join another party member, or log out.
- You will retain all game progress when you transfer and will spawn at the same location as when you left the overflow.
- The game does not offer any indications as to the size of the queue, your likely wait time, or the wait time of others who have recently transferred.
- The overflow is a separate server and in no contact with any existing world.