Cellular service needs towers everywhere to work. But many regions of the world have neither cellular towers, nor the wired infrastructure. So came satellite internet. First, a private company needs to launch a satellite into the Earth's orbit. The purpose of such satellite is to beam 4G data down on Earth. And there are a few satellites orbiting the Earth already which were launched for that purpose. Some internet satellites currently rotate synchronously with the Earth. So they are always located above the same spot over the Earth. They beam data over one continent. Other satellites are designed to fly around the Earth. Several of these moving satellites working together allows for internet access in virtually any place on the surface of the Earth, even the polar caps.
Just like with cellular towers, there is a limited spectrum over which data can be transmitted, and a limited number of channels on which devices can connect. So usage of data from communications satellites requires a monthly fee to the satellite operator or reseller. And you need a satellite phone, or satellite dish, which could send signals directly to the satellite. Satellite phones are currently quite expensive. Satellite dishes are often installed for free by the service provider, and internet speeds are getting closer to cable speeds.
Sources:
"How Does Satellite Internet Work? : HowStuffWorks." HowStuffWorks. N.p., n.d. Web. 04 Nov. 2014.