"진짜" can be translated as "really?/ That's true?" Or it just means "Real/ True"
Here are some examples to help you understand.
"그는 진짜 멋지다."
= He is really cool.
" 진짜? 와, 그것 참 이상하다."
=Really? Wow, that's weird.
"진짜웃음과 가짜웃음을 구별하는건 어렵다."
=To distinguish between the true [real] smile and the fake one is hard.