Tags are tools used to organize groups of devices within an organization. A device can be tagged multiple times making it easy to filter out devices on various levels.
For information on Tags as they relate to the REST API view this guide.
Tags can be added at the point of activation, from the Tags prompt within a device's page, or from the general Devices page by hitting the Add new tag button from the Tags section as illustrated below.
To rename or delete Tags hover over the Tag until you see the pencil icon. Click on the icon to enter editing mode.
Once in edit mode you can rename the Tag or hit the delete button which is the circle with the dash inside.