An indifference curve reflects a constant level of utility, so the consumer is indifferent among consumption combinations along a given curve. If total utility is to remain constant, an increase in the consumption of one good must be offset by a decrease in the consumption of the other good, so indifference curves slope downward. Because of the law of diminishing marginal rate of substitution, indifference curves are convex to the origin. Indifference curves do not intersect. We know that demand indicates the amount consumers are willing and able to buy at various prices.
Indifference curves indicate the consumer s willingness.
The budget line shows what the consumer is able to buy. We must have the two together to find what the consumer is willing and able to buy. The budget line reflects all possible combinations of goods that can be purchased given the prices and the consumer s budget. It is the constraint. The budget line is the individual s consumption possibilities frontier.