Basically just what the term states. A network which connects without using cable. Ok, but what is a network? A network is a system where different entities connect. In this case, electronic devices such as computers or smart phones or printers. Or all of them together. 

This network's purpose is to carry data, which is then to be used by one of the other connected devices. This data can be stored, used for calculations or printed. Whatever your device is able to do, it can with the data transported via the wireless network. 

Not so long ago, the idea of connecting one electronic device to another without using a cable, was only a dream. Well, now it's not only a reality, it's a necessity. And the technology for these devices is evolving at hyper speed. The latest devices can carry traffic or data at 9.6 Gbps, that is 9600 000 000 bits per second, whereas it used to be around 11000 bits per second. Between you and me, there are still much more than a few wireless networks running at 11Mbps. 

Early wireless networks could not defend itself against baby monitors or even microwaves in the kitchen. These days, wireless networks run on a completely new frequency, which make it much more robust against interference from day-to-day appliances and other technologies which are in use. 

So, that in very short, is a wireless network.