At the end of WW2, the USSR put puppet governments on the countries it occupied during the war with Nazi Germany; these countries were called "satellites" in the West as an analogy to, say, smaller moons revolving around larger planets. The "smaller moons" were the puppet states and the "larger planet" was the Soviet Union.
Satellite states were officially independent nations, but they were under heavy political, economic and military influence of daddy USSR. So they effectively "revolved" around it.
