@sjenningsFirst of all, welcome!
It's a very interesting question, not lame at all! Because I have been developing extensions for quite a long time and had not noticed the difference 🤣
And I can't even explain it, but looking at the documentation, like the link below,
it seems that plugin might be an older name (after all, one file included in an extension is called plugin.json). But I'm not sure, and maybe someone might give a better answer 😂
Correct - I've been using extensions from the very beginning - approximately in Dynatrace 1.117. It was mostly called plugin at that time. I believe extension is a much better name and should be used instead.