A radio service authorized by the government in the form of an issued license. This entitles one to use specific frequency bands for 2-way communication. There are more than 800,000 Ham Radio Operators in the US, and more than 3 Million world wide. Many modes are available. Morse Code, AM (voice), FM (Voice), SSB (Voice), PSK31 (Digital), SSTV, ATV, FKSK, Fax, AMTOR, PACTOR, CLOVER, ect. Up to 1500 Watts of Power on some bands.
From the U.S., I was talking to a Ham Radio friend in Argintena on 20 Meters.