When you click to add an item on the calendar, the set of icons appear without any indication to what they stand for until you click on one and see the descript

When you click to add an item on the calendar, the set of icons appear without any indication to what they stand for until you click on one and see the description in the "what" field. I know some of them are obvious, but you should think about clearing the ambiguity by having the "what" field populated appropriately as you hover over the icons.