An abreviation for the word details. Typically used in casual email conversations. Not so much in the real due to the lameness of using slang in speech.
Email to friend: Sorry to hear you lost yor phone, here are my phone numbers as you requested.
Email reply: Thanks for getting back to me with the deets, i appreciate it. Talk soon! Peace
1) Details, used as shorthand, often on the internet, and often used in the command form.
2) A "clan" of kids who used to terrorize Seattle. They called themselves Clan Deets because they would always go "Deets", or "Downtown" on Friday afternoons.