What is Ham Radio?

A small clip from the ARRL website answers it best.

Amateur Radio (ham radio) is a popular hobby and service that brings people, electronics and communication together. People use ham radio to talk across town, around the world, or even into space, all without the Internet or cell phones. It's fun, social, educational, and can be a lifeline during times of need. You can set up a ham radio station anywhere! In a field, at a club station or at home.

Although Amateur Radio operators get involved for many reasons, they all have in common a basic knowledge of radio technology and operating principles, and pass an examination for the FCC license to operate on radio frequencies known as the "Amateur Bands." These bands are radio frequencies allocated by the Federal Communications Commission (FCC) for use by ham radio operators.

For more information you can go to the ARRL website.