Get the books, read them, your understanding will increase and confusion decrease.

Both kinds of sales are "sales" as there is not just one kind. What you will see is that the popular media ("regular") sales is not actually regular, that there are also different types of sales people, and so on.

Basically your exposure and sales vocab are still underdeveloped, so reading some books will aid you greatly.

Ok, I will risk and jump in, because I am curious.

That's the spirit! Books are super cheap knowledge. When your done with those, email me and I can point you towards more for your new questions that will come up.

Do you happen to be monetizing an OSS project?

Hey, no, I have build a website with free mathematics resources for university students.

I am getting good traffic and now I am looking for monetization options that would be non-invasive to the project (for example. I don't want crappy, non-relevant adds).