Networking is a specialized field within IT so it is both hardware & software but more on the hardware side I would say. How to build, merge, extend networks and then you go on to managing and security for networks.
Back in the good old days, there were different types of networks & the topology was different for some. You don't see any token ring, 10BaseT, or even IPX any more. We had to know all that crap back then. Now it's all ethernet using TCP/IP 90% of the time.
What is it that you don't understand about wireless? It works just like wired for the most part only it send the signals over the air instead of through the wire on a specific frequency at a specific speed (a-b-g-n)
Then you have wi-max which works basically the same but is on a cellular phone frequency so it can reach for miles instead of feet.
Oh, and I always heard that it takes repeating something 7 times to memorize it. That might be true for the boring stuff. The interesting stuff comes a lot easier!
BTW--There is an acronym for memorizing the OSI layers. I can't remember it exactly now (it's been 15 years ago) but it has something to do with geeks & pizza. Give me the answer again and I can probably figure it out. Something like All Geeks Like Pizza Some Times or similar.