Hi Rishikesh,
Just one more addition to Ajay's comments; if you are creating the join by simply dragging one field in one table towards the other field in the second table then the order that you drag is important. ie: the first table you start from is considered the left table (even if you are dragging right to left!). So if you ever get confused it's best to do it how Ajay mentions. But of course it's easiest to just drag, just remember the order is important. 
-Patrick