Question: I saw the term JTB (Justified true belief).
What is the act of Justificaton ?
What makes somthing "Just" ?

Cheers
Sharon

Answer: 
"Justified" in the phrase "justified true belief" means that you have a good reason for your belief. A belief could be justified, yet false, meaning that you have a good reason to believe it, but yet it is not true. (For instance, you could believe it is raining, because it was when you entered the house a few seconds ago, yet it could have stopped in that short of a span of time --your belief is justified but false.)

What counts as a valid justification [is controversial](http://en.wikipedia.org/wiki/Theory_of_justification).
Justified true belief has less to do with "Just" in a legal moral since, and more to do with personal beliefs. 

1. Grass is Green
2. I believe that grass is green.
3. The Sky is blue
4. I believe the sky is orange.

We would on a spring day with a healthy lawn say that 2 is a justified true belief. 

For 4 we would say my belief was unjustified. 

As for the other two questions 

> 
> What is the act of Justificaton ? What makes something "Just" ?
> 
> 
> 

I'll leave those for someone else to answer, they are pretty loaded questions.