magnetic field – the region around a magnet in which another magnet or magnetic material will experience a force

To remember the meaning of magnetic field, use the following mnemonic:

The magnets in the field (magnetic field) were clearly strong because the man in the armour was experiencing a force. 

A magnetic field is an invisible region of space around a magnet or current-carrying wire where magnetic forces can be detected and where magnetic materials experience a force. This field is represented by magnetic field lines that show the direction and strength of the magnetic force, with lines emerging from the north pole of a magnet and entering the south pole, never crossing each other, and being closer together where the field is stronger and furthest apart where it is weaker. 

Magnetic fields can be produced by permanent magnets made from ferromagnetic materials iron, nickel, and cobalt, or by electric currents flowing through wires, with the strength of an electromagnet's field depending on the size of the current and the number of turns in the coil.