Isoquants:

An isoquant is a locus of points showing all the technically efficient ways of combining factors of production to produce a fixed level of output. It is also known as the equal product curve. In case of two variable factors, labour and capital, an isoquant appears as a curve on a graph the axes of which measure quantities of the two factors. The curve shows the efficient alter­native techniques of production or alternative combinations of two factors that can produce a fixed level of output

Isocost Lines:

An isoquant shows what a firm is desirous of producing. But, the desire to produce a commodity is not enough. The producer must have sufficient capacity to buy necessary factor inputs to be able to reach its desired production level. The capacity of the producer is shown by his monetary resources, i.e., his cost outlay (or how much money he is capable of spend­ing) on capital and labour, the prices of which are taken as constant, i.e.’, given in the market place.