It is a simple powered USB hub. I have an old MacBook 2,1 that has a borked screen, which I use as a desktop. Without this little hub, the sole two USB ports on the machine would be used by the human interface devices. So this allows me to have additional USB ports. The fact that it is powered allows for use with mobile external HDDs (bus powered).
It works, and I have had no issues with it. If this is something you need, this is a good product. (Though FYI the cables are pretty short).