What is Hicksian demand function?

Hicksian Demand Function:

The solution of expenditure function that is the function of (p, u) is denoted by h(p, u) and termed as the Hicksian demand function. This demand function tells us what consumption bundle attains a target level of utility and minimizes total expenditure. This function is sometimes termed as a compensated demand function. That terminology comes from seeing the demand function as being constructed through varying prices and income in order to keep the consumer at a fixed level of utility. Therefore, the income changes are arranged to “compensate” for the price variations. Hicksian demand functions are not directly observable from they depend onto utility that is not directly observable.

Demand functions defined as a function of prices and income are observable; while we want to emphasize the dissimilarity between the Hicksian demand function and the common demand function.