What is the difference between magnetic flux and magnetic force?

Answer

Magnetic field lines are lines tangent at any point to the magnetic field vector at that point. The magnetic flux through a surface is a mathematical concept that indicates how many field lines pierce that surface. The magnetic flux thus depends not only on the field line density, but also on the orientation of the surface relative to the field lines. You can compare it a bit with the flow lines of a moving liquid and the flow rate of that liquid through a surface.

Magnetic force is the physical force acting on a moving charge. In a certain part of space, therefore, a magnetic field can be present, if there is no moving charge, there is no force.