all sort of right ... sort of
there are two types of USB devices ... active and passive
active powers from the usb port
passive doesn't - it just uses the data
each USB port can talk to 128-1 devices (hub +127 devices)
the total bandwidth of that 1 port is shared between all the devices ... more than one output ... but only one input
all hubs are active and carry
[email protected] ... but again that's shared between all the ports - so a usb powered device maybe won't work.
the only "rule" - is slap it into your hub ... if it works ... ok ... if not move back one - or try powering the hub