Here's why:

* Magnetic dipole moment: This is a measure of an object's tendency to align itself with a magnetic field. It's like a tiny bar magnet with a north and south pole. Objects with a magnetic dipole moment include:

* Permanent magnets: These have a fixed magnetic dipole moment.

* Materials with magnetic susceptibility: These materials become magnetized when placed in a magnetic field.

* Moving electric charges: Any moving electric charge creates a magnetic field and thus has a magnetic dipole moment.

* Relative motion: The force on a magnetic dipole in a magnetic field is proportional to the velocity of the dipole relative to the field. If the object is stationary relative to the field, there is no force.

Key points:

* Not all objects experience a force in a magnetic field. Only objects with a magnetic dipole moment and relative motion will experience a force.

* The direction of the force depends on the direction of the magnetic field, the direction of the magnetic dipole moment, and the direction of the object's velocity.

* The strength of the force is proportional to the strength of the magnetic field, the magnitude of the magnetic dipole moment, and the velocity of the object.

This is a fundamental concept in electromagnetism, and it explains how electric motors, magnetic levitation, and other important technologies work.