What is the difference between Jhana and Samadhi? In Sutta pitaka we find two Suttas namely Jhana sutta and Samadhi sutta.
 What is the difference?

http://www.accesstoinsight.org/tipitaka/an/an04/an04.041.than.html

http://www.accesstoinsight.org/tipitaka/an/an09/an09.036.than.html
Samadhi is a general term for concentration. Jhanas are stages you achieve in Samatha meditation when your concentration reaches a certain level. 

To give an analogy, Samadhi is like the temperature of ice. When the temperature reaches a certain level, it becomes water. That's like reaching the first Jhana. If you keep heating, it will become steam. That is like reaching the second Jhana and so on.