Use The Category From The Previous Item Added

With this option turned on, when you add an item through the item entry process and save the item, the next item you add will keep the category you last used.  You can still select another category, but this helps facilitate fast item entry, if you adding the same types of items together.  

With this option turned off, the category will be blanked out when you save your item so that the a new category must be selected on the next item you add, in the item entry session.