Akg Wms

Does frequency matter with a Wireless Guitar system?

I’m buying one for my boyfriend for christmas this year- I already have one all picked out.. the AKG WMS 40 Pro Wireless Guitar System

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&Item=200277171151&Category=100230&_trksid=p3907.m29&_trkparms=algo%3DLVI%26its%3DI%26otn%3D1

but does the frequency I pick matter? I don’t really understand what the differences between frequencies are?
thank you, how would i find out [...]