hello
sorry if this is such a noob question. I just want to know what the "mailman" is for under "Tweak settings" in whm. If i disable it, what will happen? What are the pros and cons of disabling it?

Mailman is a piece of software used for creating and maintaining a mailing list. If you disable it, then users on your server will be unable to create mailing lists within cPanel.
What are you using the server for? If it's web hosting related, I would leave the mailing lists enabled.

its a personal vps. but if i disable it since i wont be creating any mailing lists, i can still send and receive emails right?

Yes, this is for setting up mailing lists, and has nothing to do with ordinary day-to-day email sending. If you're the only person using the box, and not planning on setting up a mailing list using it, go ahead and disable it. No point having the thing run periodically if you don't need it.