In circuit elements what is the use of inductor?

Inductors are used for several reasons, mostly to do with AC and DC. An inductors` Reactance (similar to resistance in Impeding the flow of Current) rises with frequency. Hence an inductor can be used to pass DC but choke off the AC (RFC, Radio Frequency Choke). It can be used with a Capacitor to form a Resonant Circuit, which peaks at one frequency and can eg be used to select the Radio Station one wishes to listen to, and reject all others. Other connections can yield Filter or Diplexers, Transformers and many other uses, like Power Factor Correction.