How is earth's magnetic field like the magnetic field of a natural magnet?

A magnetic field is induced by the movement of electrons.

In an electromagnet, the flow of current ensures this.

In a permanent magnet; there is a grouping of 'magnetic domains' in which the alignment of the spin of a group of electrons is similar; will produce a permanent magnetic field. In this case the movement of the electrons is their property of 'spin'.

The Earth's magnetic field is generated by the net sum of electric currents generated in the mantle, produced by movement of the hot materials.

Note, that the 'Curie Point' (discovered by the Curies), is a temperature above which a magnet may not hold its magnetism. The thermal disorder takes precedence over the previous alignment of the electron spins.

Because of the Curie Point, there is no possibility of a permanent magnet existing in the interior of the Earth and causing the Earth's magnetic field.

The Earth's magnetic field varies with time, and has reversed its polarity on several occasions. It also varies somewhat with the effects of the charged 'solar wind'. When there is a 'mass coronal ejection' and if it happens to face the Earth at that time, the Earth's magnetic field will be severely disrupted.

In the 1859 'Carrington Event' such a storm caused much damage to the electric circuits of the day. Such an event today could well essentially destroy modern civilization.

One such Coronal Mass Ejection occurred on July 2012, but fortunately was pointed away from Earth.