The USB port on the back of your Cricut serves two key purposes:
1. To allow you to use your Cricut with a computer and software programs like Cricut Design Studio, Sure Cuts A Lot or Make the Cut software products.
2. To allow you or the manufacturer to update your Cricut's firmware. This is a key method of providing Cricut owners with performance enhancements and fixes to the internal software on the Cricut machines.