The short answer: It is dependent on what it is, an arrangement of electrons in a metal that has an effect on other electrons nearby.
The long answer depends on why the electrons are arranged that way: Electrons are designed to work as pairs like our hands. If you bring the palms of your hands together notice that all the fingers match but if you put the palm of one on the back of the other the thumbs are pointing in opposite directions. When the palms are brought together with the fingers pointing in opposite directions the thumbs are also pointing in opposite directions. Some people are sensitive enough to feel the slight resistance when bringing the hands close together with the thumbs aligned. There is a slight resistance just before they touch. Also a tendency to grip each other when the thumbs are not aligned. Massage therapists like myself take note of that field difference when placing our hands and magnet therapists when determining which pole of the magnet to place in the different biological fields.
So why multiple poles and opposite fields on each side or end?
Some therapists are very insistent on only using magnets with the thumbs pointing one direction designated negative. Why will be apparent when I discuss what can be observed while using magnets therapeutically. The field repels itself and is attracted to the opposite field. This force rapidly becomes weaker over distance. At the edge of the pole of the magnet the field will curve and try to return to the opposite pole of the magnet. This allows magnets to be placed side by side with poles in opposite directions. The field traveling the short distance between poles then becomes very strong. Using the illustration of the hands all the unpaired electrons will want to point their thumbs away from one pole then sideways to the other pole then back down to the other pole. So what difference does it make?
My observation: When applying a negative field to the body retention of fluids is reduced and applying a positive field it increases. The effect could be compared to applying heat and cold which is in effect phototherapy, infra red being radiated or absorbed, It is well established that water changes its structure in a magnetic field. Other compounds may also change.
My uncle's observation: Back in the 1950s after he was released from working on the atomic bomb to return to university research on synthetic organic materials, he answered my mothers question of why synthetic vitamins were not working the same as synthetic ones. His explanation was that compounds formed by photosynthesis have folds that are based on the thumbs pointing one direction and those produced by chemical processes have thumbs pointing the opposite direction so they fold into proteins that are chemically the same but physically a different shape.
Conclusion: our bodies are operating on a designed structure of form and energy transfer based on photo electric magnetic chemical processes. By being observant we can now turn photons into electricity [solar panels] and electricity into photons [LED]. Let us use the same level of observableness of the effects of magnetic fields to produce function in dysfunctional tissue.