Magnetism is one of the odd forces in nature, along the lines of gravity. There are no particles that we call Magnetic Particles, and you can't see it, but you can measure it.Also odd is the Lines of Force that is seems to manifest itself as.
Transformers and magnetic coils are so important in most of our devices that you have to know a few things about magnetism:
There are turns of a conductor (usually copper) on a magnetic core (usually iron), and the Magnetic Lines of Force are mostly confined to that magnetic core but not stored there.
When a coil has a current running through it, Magnetic Lines of Force are created and expand in intensity as the current increases. That expansion is why coils tend to smooth pulses or variations of current - hence the "Choke". When the current is cut off or reduced, the collapsing Magnetic Lines of Force cutting across the conductors creates a current going in the opposite direction or of the opposite polarity. This is put to use in various instances (Switching Power Supplies), and is a problem in others (Motors).
Other wires in the same Magnetic Lines of Force also have currents (and voltages) induced in them, which is used in Transformers of all types. We use transformers to convert high voltages to low ones, and low voltages to high ones. Transformers only operate on varying voltages. If the voltage (or current) is steady, Magnetic Lines of Force are steady and nothing changes.
Guitars Pickups work because the Bias Magnet on the Pickup create a Magnetic Field (Magnetic Lines of Force that are outide the Core) and the steel strings disturb this Magnetic Field. The corresponding varying voltage is the signal that travels down the guitar cable and into the amplifier.
Most people have seen or played with magnets, and noticed that one end of a magnet is attracted to another magnet, and the other end is repelled. That is another mysterious quality of Magnetism - Like Poles Repel, Opposite Poles Attract. This is called Polarity.
Speakers work because varying currents in the Voice Coil that is within the Magnetic Field of the speaker's magnet structure cause the Voice Coil to move as the Magnetic Field from the Voice Coil is the same Polarity as the speaker's, and then the opposite, causing sound to be produced.
So you see, Magnetism has a vital role in a whole lot of things we use every day.