Flow control is what commincations devices use to talk back and forth (simplified version).
So basically, if your computer wants to talk to the wireless network, the computer could tell the network that it is free to accept data... and the network can tell the computer when it is free to accept data.
There are other carrier signals they can set as well, ie: busy, clear to send, clear to transmit etc...The general rule of thumb is: if it is working, then dont change it. 
General flow (for serial (RS232 etc) are Xon/Xoff, Software or Hardware. I'm not sure what protocols they use in wireless tho...
Hope that helps... 