Doujin = manga?

I'm not weaboo enough to know this, but I know the wrath of said weaboos can be lethal if I get them mixed up. So before I share some that I have with 4chan I must be prepared.

So, what's what? Is a doujin a manga but a manga not a doujin? Dictionary.com was not very helpful.

One more question while I'm at it. Do you say it like "doh-jinn" and "mahng-gah"?

Doh-Jee-N.  Ma-n-Ga.  And Doujin are fan manga.

Doujinshi are fan made comics.

So yah, doujin = manga.

Did someone just say...