Variable Inductors:

A variable inductor is the one whose inductance may be charged over a specific range as and when required. The inductance is usually varied by changing the position of the core with respect to winding.

Preset Inductors:

Preset inductors are a variable inductor that is varied and then set for the most optimum performance. An application of a preset inductor is in Intermediate Frequency Transformers (IFTs) utilized in radio and television receivers where the inductance is varied by moving the core to get the wanted IF response curve.