Hi Alex, No, it isn’t slang. It is an entirely standard word meaning something “placed deeply within something else”. You know how when you are in bed you are under the sheets, comforter, and blankets and “within” the middle of the mattress under all that? That’s the idea. So you can have little diamonds embedded within the metal of a necklace, for instance. People who are put deeply within certain kinds of teams are said to be “embedded with” the team. We use it to talk about journalists put inside military units, for a notable example.

I don't usually recommend this dictionary but it gives a good enough definition for the common situations. https://www.thefreedictionary.com/embedded to be firmly fixed into something, to be enclosed surrounded by something, to be or become an integral part of something. applies to viruses and objects and cells and people and other things.

As far as I’m aware it means “placed”. :)