Tags are used to "categorize" campaigns. You can manage your tags under "User Area > Manage > Tags" section. You can add and remove tags to the system.

In order to assign campaigns to tags, simply go to campaign list ("User Area > Campaigns > Browse") and select campaigns you wish to assign to a tag. Then move your mouse to "Actions" list option and select the tag you wish to assign.

In order to filter your campaign list based on tags, move your mouse to "Filter" option and select tag(s) to filter the list.

Tags are useful if you sending different kind of email campaigns such as monthly newsletters, update notification emails, system alert emails, etc.