Simplify the following text for a Grade 7 native English-speaking person.
Original: Amateur radio ( ham radio ) is the licensed and private use of designated radio bands , for purposes of private recreation , non-commercial exchange of messages , experimentation , self-training , and emergency communication . Amateur radio , like other regulated radio services , operates under rules that limit the maximum power and the technical and operational characteristics of transmissions .
Simplified: Amateur radio is often called Ham Radio .