Simplify the following text for a Grade 5 native English-speaking person.
Original: The first four series were called Digimon : Digital Monsters in international markets , whilst Savers was released as Digimon Data Squad .
Simplified: The Digimon are often used for evil by the main villain , depending on what season of Digimon . In the first season , the digimon are controlled by Black Gears .