Magnetic induction is the magnetic field induced in a medium by a magnetic field strength at a given point, denoted as B, measured in gauss (Gs, CGS unit) or teslas (T, SI unit), 1 T= 104 Gs. It is the vector sum, at each point within the medium, of the magnetic field strength and resultant polarization strength. Magnetic induction is also defined as the number of flux line per unit area normal to the direction of the magnetic path. 

Magnetic polarization strength is also called intrinsic induction, denoted as J, measured in gauss or teslas. It is the vector sum of the magnetic dipole moments of a unit material. It indicates the vector difference between the magnetic induction in the material and the magnetic field strength. This relation is expressed by the following equations:

B= m0H +J      (SI)    (1-1)
B= H +4pM      (CGS)   (1-1a)

Where 0 is the magnetic permeability in vacuum. In CGS unit, μ0=1 Gs/Oe, while in SI unit, m0=4p´10-7 Wb×A-1×m-1 (webers per ampere and meter). M is known as magnetization, similar as polarization J, representing the vector sum of individual atomic magnetic moments per unit volume, and there has J=μ0M.

What is Magnetic Field Strength?
 
Magnetic field is a physical phenomena induced by the motive electric charges in their surrounding space. Magnetism of materials arises from two atomic sources: the spin and orbital motions of electrons. Therefore, the magnetic characteristics of a material may change as a function of alloying constitution. Magnetic field strength is the measure of the vector magnetic quantity that determines the ability of an electric current, or a magnetic body, to induce a magnetic field at a given point, denoted as H, measured in A/m (amperes per meter, SI electromagnetic unit system) or Oe (oersteds, CGS electromagnetic unit system). One unit of A/m is defined as the field strength value induced by an infinite long linear conductor bearing one unity ampere electric current that locates 1/(2π) meters away from the measured position. 1Oe=1/(4π)×103 A/m.