Throughout the iForest world you will find markers. These are small devices that serve no purpose other than to let a player say "I was here".
If you can find the appropriate marker key, you can claim a marker as your own, at which point a little flag will show everybody that you own it.
If somebody else has already claimed that marker and you claim it for yourself, then your flag replaces whoever's was there before. You can check on the status of various markers in the game by going to the live section.
