Hello aspirant

It is an economical word The term was first introduced  by Alfred Marshall in his principles of Economics

. Derived demand for a factor of production or intermediate good that occurs  as a result of the demand for another intermediate or final good. The demand for say a factor of production by a firm is dependent on the demand by consumers for the product produced by firm.

It is demand for some physical or intangible thing where a market exists for both related goods and services.