We will call \(\vec B\) field as magnetic field when no medium is present.\\ In presence of a magnetic medium, \(\vec B\) will be called magnetic flux density or magnetic induction. The field \(vec H\) will called magnetic intensity or magnetic field intensity
The field \(\vec B\) is a fundamental in the sense that it is this field that appears in the Lorentz force equation.
The properties of magnetic materials are described in terms of a field \(\vec H\). This field is average of \(\vec B\) field in a magnetic material and should not be confused as being fundamental.
In absence of a medium, the two concepts coincide and can be used interchangeably. Different conventions are used for these fields by different authors. We will continue to use magnetic field for \(\vec B\) field when no medium is present.
In presence of magnetic media, the \(\vec B\) will be called magnetic flux density, or magnetic induction and the field \(\vec H\) will be called magnetic intensity, or magnetic field intensity.