They are literally plug and play devices. Those made by renowned manufacturers also come with easy to understand manuals.
There are mobile network operators who provide bundled services using this technology. They offer a router, an USB modem and a home or office broadband connection at a monthly subscription fee. This has provided an alternative solution to households who cannot obtain good quality land line connections. Of course, the performance of the mobile connection relies on the investment and management in network equipment by the network operator.