Tags are categories that are assigned to your time entries to make them meaningful. Tags are reflected in reports, allowing you to view reports and dashboards filtered by tags. Tags are universal for the whole team and can be set up and managed by team managers and owners.
Tags can be set up in various ways - based on projects, clients, or internal groupings - and can be set up to automatically tag your entries based on keywords. Managers can add an unlimited amount of keywords to a tag, to ensure that the majority of entries are automatically tagged if possible. For a tag (2) to trigger automatically, the keyword (1) must appear in the window title.
If a tag is not automatically applied, there are a couple of quick and easy ways to add tags to your entries.
Tagging individual rows
To add a tag to an individual time row, simply click the 
icon next to the entry and select the tag you would like to assign.
Tagging multiple rows
Groups are the fastest way to tag entries. Any time entries that you add to a group will automatically get assigned the group tags.
To assign tags to multiple rows, select all the rows you wish to tag. The rows will appear in the action pane on the right side. Click on the tag button above the description box in the action pane and select your tag(s).
You can have multiple groups open throughout the day, so for example, you could set up groups for each project you are working on, and when you are ready to post your time, simply go through and select the time entries required, add them to the corresponding group and they will automatically be assigned the correct project tags specified in the group. You can add to the group at any point throughout the day as the group will remain open until you post it. Note that groups do not carry over from day to day.