In the Elder Scrolls Online Update 36, released alongside the Firesong DLC, the ability to mark targets for the group was added to the game.
This guide will explain how target marking works.
How to Mark Targets for your Group in ESO
To begin with, you need to hold down the tag button to open the target marking wheel. By default this will be the tab key on mouse & keyboard, or D-Pad Right on a gamepad.
You can then select an icon to assign to whichever target you are currently looking at. The tag can be assigned to any enemy, other players and also most NPCs. You can also tag yourself by selecting an icon when not looking at a valid target.
The marker will stay in place until you remove it or the target moves too far away.
To remove the marker, simply repeat the step while looking at the same target, and reselect the marker that you want to remove. Alternatively you can change the marker assigned to a target by simply opening the wheel again and selecting a new one. You cannot have more than one marker assigned to a target at a time.
You are currently not able to mark locations on the ground with this method, it can only be targeted at characters or enemies. This is a useful tool for helping to coordinate in your group, particularly in dungeons, trials or PvP.
We hope you found this guide about group tagging and target markers in ESO (Elder Scrolls Online).