What is magnetic relunctance?

Reluctance is the opposition offered by a magnetic circuit to the formation of magnetic flux. It is equivalent to resistance in an electric circuit.

Reluctance is the ratio of a magnetic circuit's magnetomotive force (measured in amperes) to its magnetic flux(measured in webers, pronounced 'vay-bers'). So, reluctance is measured in amperes per weber (which is often 'spoken' as 'ampere-turns per weber'). This is equivalent, in an electric circuit, to the ratio: electomotive force to electric current.