'진(眞)' is borrowed from Chinese (real, genuine), and '짜' is a pure Korean suffix that transforms the word to pretty much anything. (adjective, adverb)
It's actually a slang, thus you won't find it in official documents.
Below are some often used words with '진':
진실(n): genuine + fact(reality) = truth
진품(n): genuine article
진심(n): genuine + heart(mind): this one is tricky since it doesn't exist as a noun in English, the closest one being the adverb "sincerely" which in turn would translate to "진심으로"
진심이야?: no kidding?
네, 진심입니다: Yes, I'm serious about this (I mean it from the bottom of my heart)
Now you know four Chinese module words that will be very handy over the course of learning Korean. (or even Chinese or Japanese with slightly different pronunciations)