A Track Event is a one-way signal that will allow you to further leverage the interconnectivity of Track View with other systems. In the case of Track Events, that system is Flow Graph, as you can send this signal to branch Flow graph logic from a Track View sequence.
Each sequence may have any arbitrary number of Track Events defined. These events can be called at any time from a Track Event Node. Each event may also carry with it a string value assigned to the key frame in the Track View editor. When a Track Event is triggered from the sequence, its corresponding output port in a special Flow graph node is activated, allowing you to branch Flow graph logic very easily.