The barcode scanner is for speeding up inventory item Name data entry. For example, if you have a 15 oz can of Kroger Black Beans, instead of typing all that in via your mobile phone's on-screen keyboard, you can scan its barcode and it will enter "Kroger Black Beans, 15 oz" into the current item's Name field, where you can further edit it.
The scanner's data comes from one of two on-line UPC barcode databases, so you'll need internet turned on for scanning.
Opening the Scanner
From the Inventory Tab
Add a new inventory item by tapping the + tool from the Inventory tab:
In the resulting item search dialog, tap the barcode icon to bring up the scanner.
From the Item Details Screen
You can also access the scanner for an existing item, by tapping its Name from the Item Details screen:
Then tap the search icon:
And finally, tap the barcode icon to bring up the scanner:
Once the scanner is up, position the barcode as shown below:
Be sure to provide good light on the barcode for best scanning performance.
You may have to move the barcode a little closer or farther away from the camera, but the scan should eventually complete:
The app will then search the UPC barcode databases to find the name, and optimally the size, of the item, and populate the item's Name field: