An item is something that is being collected and or delivered on a job, this is used for Proof Of Delivery and Collection customers.
For example, if you are a waste recycling company you may be collecting some bins of waste, this is where you can input it. When you are going through a job on the application you will have the option of "add parts", "remove parts" or "change quantity".
The portal users can pre-allocate some parts when they are booking the job, if they know what is being collected or delivered. If not you can add the item(s) on the device (this will then upload the information up onto the web portal).