Isoquants represent combinations of two input factors that produce equal levels of output. They are downward sloping curves that do not intersect, with higher amounts of one input substituting for lower amounts of the other input. The marginal rate of technical substitution measures the rate at which one input can be substituted for the other while maintaining the same output level. Isocosts represent combinations of inputs that cost the same total amount, with higher isocost curves corresponding to higher total costs for a given output level. Isoquants illustrate technically efficient combinations of inputs while isocosts show financially efficient combinations for a given cost.