with wifi tethering on your phone you can tether up to 5 devices i believe. that includes any smartphones, tablets, laptop computers and even desktop computers. your phone basically acts like a router in your home. you have to be subscribed to the tethering plan or root your phone to use this feature without subscription (you're already paying for your data anyway)
last time i heard there are a few tethering apps not requiring root. you may want to check some threads on this forum.
Tethering is different than hotspot. I'm used to BB, which handles tethering a little differently. A tablet or laptop can connect through a BB via bluetooth using tethering. Hotspot uses WiFi, not BT. If connecting a BB with a Playbook, there is also a 3rd connection option, Bridge (which is also BT, but doesn't require turning on any settings). Tethering speeds are slower than hotspot and faster than bridge, but tethering uses much less battery drain than hotspot. It also frees up all your BB device functions for use while tethering (some functions are limited while a phone serves as a hotspot).
It appears there is no such tethering option for the Skyrocket - tethering through it requires a physical USB connection. I haven't found a way to use it via bluetooth. It seems like the Skyrocket is pretty quirky when it comes to BT. But the hotspot is screaming fast