your backup battery is also a surge protector, when you plug in your data cord (telephone or network cord that comes from the cablemodem/router) it will protector your laptop data port from surges that can happen when a lighting hits nearby
(a few years ago a lighting hit within 2 blocks of my house frying a few things including the cablemodems that also fried the network port of the switch they were attached to)
the USB cord does two things
a) it allows you to use the software that comes included to control some settings in your UPS through the computer (such as disabling the beep and others)
b) it also allows the UPS to safetly shutdown the computer during an outage if you configure it to do that
