That's a tough one for a lot of people, and ultimate there are so many different schools of thought. I found this online, which is easier than trying to explain everything, but this is a decent (if dated) sort of starter-template for what a db-schema could look like. Gives you an idea of some of the more rudimentary functions or a forum and how they correlate.
Of course, there are people far better versed than me who I'm sure can explain it in detail, and give you better examples, but hopefully this is enough to give you a starting idea of what's what.
Thank you for getting back to me! I tried including a link to my db schema, but it seems my account doesn't have permission to do so yet. Is there another way I can send an imgur link?