What is the difference between OK and all right?

OK- This roughly means "YES''. It expresses agreement or acceptance. This is equivalent to American "yep'. Indians use OK very frequently, just to make sure everything is OK. But people now a days tend to use it as a verb too. Eg. He okayed it. This means, he approved it. 
 
all right - This means it is satisfactory. Mostly used as an adverb. Eg. The work is all right. Only just good enough. Excellent కాదు. పరవాలేదు అని అర్థ్ధం.
Eg. "What did you think of the movie?" "It was all right. Nothing special."
The food was all right, I suppose, but I've had better.