When you add a new inventory item or menu item, you will be asked to define the purchase unit and the shelf unit. There are thousands of possible variations that may be used, so TPP allows you to create any custom unit of measure you need for your business.
Unit measures define units that inventory is broken down into.
Ex. case, bottle, pound, ounce.
These can be edited under Admin > Custom Lists and then choose Unit Measures from the drop down.