A tracker is each one of the accounts that can be tracked, they are the same as a Twitter account. For example, if someone wants to track the Coca-Cola brand on Twitter, they will have to set a new tracker for @CocaCola. From that moment, the Twitter User Tracker will start to collect data, which will be updated every hour.
Many trackers can be grouped under a tag. A tag groups and compares several trackers. The metrics inside a tag file can be compared. Following the Coca-Cola example, the tag “Beverage brands” could be created to group the tracker @CocaCola and @Pepsi.