xbee/synapse RF engines

Hello, I'm new to the arduino programming and robotics. I know a bit about the standard r/c controllers (for airplanes and cars) and am used to being limited with "channels" 2,3,4,6 etc. My question might seem basic but, how many channels can be utilized with an RF engine like the xbee or synapse modules? Or is there really a limit? And same question in regards to a "wifi" wireless setup? I've tried to search for the answer online but have been unable to get a clear explanation.

Thank you in advance for any help on this

My question might seem basic but, how many channels can be utilized with an RF engine like the xbee or synapse modules?

Shouldn't you be asking digi.com that question, for the XBee?