I bought this product in order to output my [much larger] mixer to a PC via USB. This unit is powered by USB, so can be plugged in to the included wall socket adapter and used as an input for speakers, but also can be powered straight from a computer by the USB, enabling you to input into the PC without having to have it plugged into the wall.
The way that I use the Xenyx 302 USB is having my main mixer's RCA audio output connected to the LINE INPUT on the Xenyx. There is a headphone output which allows you to hear the mix and then I have the USB cable plugged into the computer. I can then record the whole live mix of our band through the PC.
Alternatively, this unit can be used for recording pod casts with it's microphone input or a guitar and microphone for a singer/songwriter.
It is a very versatile product, especially for its size and price and I recommend it to any person looking for more options whilst recording.
As a side note, the product is made even better by the fact that it comes with a licence for Tracktion recording software. This is not actually mentioned by thomann, but by going to Behringer's product page and registering your mixer's serial number, Behringer and Tracktion give you a licence for the software. This negates the necessity for a decent software as Tracktion is pretty useful. This is particularly good if you are a beginner at this sort of thing and are only using free software.
TL;DR: The Behringer Xenyx 302 USB is a useful bit of kit that comes with some decent software.