ok...here we go...
Dual speed means that it supports both 10mbit and 100mbit connections, could be uplinks at 10/100 or 100 and normal ports at 10 or each port autonegotiates with 10/100.
A switch is superior to a hub since it will not let signals bounce into each other (collisions). It only lets one packet through at a time, essentially the analogy of a single file line going through a doorway, rather than everyone trying to cram through at the same time. The unmanaged part means that you just plug it in. Managed hubs/switches allow some form of bandwith management in terms of priorities normally of protocols or what ips get bandwith priority.
Hope that helps...that switch is pretty darn cheap. I've learned from experience that the cheaper stuff is garbage...look in the deals section at good switches like the netgear FS108 which is well worth the extra $20 after rebate. Good luck.