Simple Question, can someone please tell me what the acronyms mean?

I know this may be a "stupid" question, but everyone uses acronyms that I can sometimes figure out - but not all of them.

Can someone please tell me what they all mean?? Such as DH, OP for example - is their a list on the site?

I know MIL, FIL, AL, MC, etc - but not all the others.

Thanks for understanding ❣️