G'day Kayla,
I am pretty sure you are not overthinking, it is apparently a common point of confusion. I hope that the article I am including helps to clarify it. Below is the link and the item within that page that might be relevant. The nutshell answer is that it is not a methodology, however it does include methods for you to apply where appropriate.
zenkit.com/en/blog/7-popular-project-man...yre-best-suited-for/
Specifically, check out number "7. PMI/PMBOK" might help. It's a bit too long to patch in here.
Let me know if this helps,
Linda