What do the upstream/downstream USB ports on a monitor do?

I came across few configuration of a monitor and they include many different port along with some USB ports.

Monitor: DELL P2214H, DELL P2414H

In the monitor description it mentions that there are both USB 'upstream' and 'downstream' ports. What is the difference between these and what are the uses of each type? Can I connect a speaker directly to the monitor?

Solution 1:

On a monitor like that with USB ports, there is a USB HUB in the monitor itself. a USB hub has to have an input from the computer first.

http://en.wikipedia.org/wiki/USB

The TypeB the squared up connection is the input for the hub, a cable similar to a printer cable with a Type A plug on one side, and a Type B plug on the other side will be used to connect the computers USB port, to the hub. The hub will then have multiple ports.

Once you have an input run from the computer, the "HUB" will provide the USB ports. It will draw its power from the computer connection. Any USB connecting device would work in it, as long as it stays within the power specs.