A trivial answer of the question is that wireless broadband is broadband without wires, so if you have a wireless network in your home that uses a router than connects to your computers and other devices with Wi-Fi, then you are already using it, though really that is wireless networking. You connect to the internet over a telephone line using ADSL and that connection is shared amongst all devices on the network using radio waves.
What is Wireless Broadband?  

What we also mean by wireless broadband is connecting to broadband when you are away from your home, for instance when you are using a laptop, tablet computer, or smartphone and connecting to a Wi-Fi hotspot. Wi-Fi hotspots are available in many locations, for instance in many pubs and cafes.

And finally, wireless broadband can also refer to broadband services that are provided by a mobile network provider over mobile networks and to which you connect directly through a smartphone or a 3G broadband dongle that you plug into your computer.

You can also connect a wireless router to the internet using a similar dongle. In this case the internet connection is made through a mobile network and shared with all your mobile devices using Wi-Fi technology.Which of these is the best broadband depends on a number of factors, and many people use a combination of them. Most people connect to the internet in their homes over a telephone landline or through fibre optical cable. In the latter case fibre optic cable may be supplied directly to their home, though in most cases it is supplied to a junction box which serves a small area, and the final connection between the junction box and the home is over wire. In order to share the connection with other computers and devices in the home Wi-Fi is by far the most popular method, though this might not always be possible as the Wi-Fi radio waves are attenuated when they pass through thick walls; in which case a Wi-Fi range extender may help.

Having the ability to connect directly to a Wi-Fi hotspot is the cheapest option when on the move; in fact generally it is free. The reason that many cafes and pubs make them available is to attract your custom but all you need do is buy a coffee or half a pint of beer and you can sit there online all day. The problem with this is that it is not always possible to find a Wi-Fi hotspot when you need one.

Connecting the broadband through a mobile network provider is certainly the most convenient method when on the move. Obviously you need a contract or pay as you go deal with a provider and you can use an existing contract or you can take out a separate deal just for broadband.

Teaming a mobile broadband dongle with a mobile Wi-Fi router can be an ideal solution for people who travel frequently. The problem with just using a dongle attached to a laptop is that the signal can be very variable, say when travelling on a train. If the router with its dongle is located high up in the luggage rack or against a window the broadband connection can be much more reliable.