The tree list displays all of the maps available to you both from our servers and from your local mods folder. It also displays any custom groups you've created.
Each item in the tree list has lots of visual indicators of status for the map. The solid color on the right of the tree item indicates the state of the map (ex. Installed, Corrupt, Outdated, etc). If there is download/install progress available for a tree item, it will be shown as a thin progress bar below the map's name.