Tags allow you to later filter your customers and leads to perform analysis and actions on them. Tags originally did not have an associated time stamp on them, but all tags going forward will. This allows you to do things like make advertising campaigns that tag your leads and then later filter to see how many lead came in from that campaign during a specific period.
There is also a tag page that will allow you to add, edit, delete, and organize your tags and the customers they apply to. To learn more, watch the video below.