An indifference curve, with respect to two commodities, is a graph showing those combinations of the two commodities that leave the consumer equally well off or equally satisfied—hence indifferent—in having any combination on the curve. 

• Indifference curves are heuristic devices used in contemporary microeconomics to demonstrate consumer preference and the limitations of a budget.  
• Economists have adopted the principles of indifference curves in the study of welfare economics. 

Source: TMH Ramesh Singh