Journal
One of the final features that was included in Pokemon GO was the addition of your personal journal (found directly in your Player's Main Profile). With it, you can view all your recent activity and exactly what you have done as of late. This includes recent Pokemon Captures, Eggs Obtained, Gyms Battled, and PokeStops Visited (and what items were received fro them). It isn't necessary at all, but if you're someone who would like to keep track of where you have been and where you may have caught a certain Pokemon, your Journal will allow you to do just that.