What is this?
Satellite phones are similar to your mobile phones. They let make you phone calls from almost anywhere on the earth. Its communication does not rely on terrestrial cell phone networks or cellular communication. Instead, satellite phones beam their data directly to and from satellites (those are orbiting the earth).
Based on their functionality we can say a satellite phone is a phone that uses satellites for communication (for sending and receiving data) instead of terrestrial lines. Typically, these gadgets are enabled communication all over the world irrespective of location whereas normal cell phones require proper terrestrial network coverage to enable communication.