For some people, these two games/animes/mangas/trademarks etc. are like night and day, but still many don't know which one is which. The purpose of this here discussion is to find out how to explain the differences and similaritises, especially for outsiders. You can list everything from major directions to minor details. And if you see someone mistaking here, feel free to point out, of course.

Some I noticed, correct if wrong:

Origin

Both are from Japan. Pokemon is originally a game for Nintendo's Game Boy handheld console, mostly based on an idea by Satoshi Tajiri of Game Freak. The first Pokemon games Pokemon Red and Pokemon green came out in 1996.

Digimon, on the other hand, is originally a tamagotchi-like game released by Bandai in 1997.

World

Pokemon games, TV series etc. take place in an ecosystem different from ours in that it has creatures called Pokemon. There exist also humans, normal animals and plants. The geography is based on the real world, in Mewtwo Returns we see the world map as we know it and, more notably perhaps, we see the map of Japan in the games. The towns and other places have taken different names from our world, except for some like Kanto (a Japanese province) and Hollywood (mentioned in the anime episode Go West, Young Meowth). For example Coldenrod City is believed to refer to Osaka and Ecruteak to Kyoto.

Digimon is situated in two worlds, the real world (sometimes called 'Genjitsu no sekai' in Japanese) and Digital World. The real world has all the real place names ranging from Australia to Moscow. Digimon live naturally in Digital World, but for example in the end of the second season they invade real world. Moving between the worlds happens through 'Digital Gates'.

Your turn.