Scroll down a bit in this article. There’s a list of what each of the available keys are required to provide. A “key” in this context is basically a notch in a certain location, which then defines the meaning of the various pins of the connector. Some devices have multiple keys, as some of the specifications have a common subset. Like key A+E is common, because E provides almost everything that A does, so a device that only requires the common interfaces can work in both. Cars that rely on one of the exclusive interfaces will have the specific key of course. This A+E communication is often used for WiFi cards.
Sockets always only have one key though, for obvious reasons.
Edit: correction/clarification
I’ve used windows since the 90s. Not once have I intentionally used WordPad.
It did open by default for some file types for a long time (.doc), usually mangling the content cause it couldn’t actually handle them properly. I think it was also the default for .txt files at some point, causing many curse words when editing plain text files, that invisibly weren’t so plain any more after… Programs expecting a configuration fine really don’t like that sort of thing.
So: I’m very ok with this. Just install LibreOffice or something if you needa Word-like experience. Install notepad++ for anything “plain”.