Quoted By:
They're two very different things. Ignore the fact they're both Japanese, about monsters, end in -mon and peaked in the West at the same time.
Digimon is set in a different dimension where children are brought into a power struggle between good and bad. All their goals, the tags, the black gears, it's all about their friendships with their Digimon and the fact that they want to help them save the Digiworld. Each kid has one Digimon (originally, anyway)
Pokemon is in a world where Pokemon are an accepted thing. They basically replace animals. People use them for livestock, pets, whatever. You, or Ash, take the role of a kid who wants to raise a team of Pokemon, battle with them to attain badges and become the champion. It's about competition, fun. Naturally there are antagonists, but they're not the main plot point, it's about the badges.
Two very different worlds, if you look at them.
Fuck, I need sleep.