Activity Types enable you to quickly identify certain kinds of activities, by using types like "Fundraiser", "Party", "Luncheon", etc.
Note: You cannot delete a record that is in use. One solution is to create an entry called, "Undefined" or "Unknown" and merge the unwanted entries into that one.
1.On the Home ribbon, choose Lists from the Settings section.
2.On the System Lists window, expand the Activities section.
3.Choose Activity Types
4.Modify the list as needed.
Entries on this list can be combined into one. See Merging/Combining Values for details.