All magnetic fields are a consequence of electric currents.

A magnetic field is a region of space in which a magnetic material experiences a force.

A magnetic field can be represented by field lines that show the shape of the field. Lines close together represent a strong field and lines widely spaced represent a weak field.

Field lines are always complete loops. We draw them in the direction from a north to a south pole. [The direction of the field is the direction of the force that would act on an isolated north pole placed there.]