Particle physics basically deals with things that are smaller than atoms – that is, subatomic particles.
Many subatomic particles are made of smaller particles again. If you try to break a particle down into its constituent pieces, you eventually reach a particle that can’t be broken down further (as far as we know!) These basic units are called fundamental particles.
For example, if you start with an atom of carbon, you can break it down into six protons and (usually) six neutrons. (About 1% of the time, carbon can have a different number of neutrons.)
There are also electrons buzzing around the outside. The number of electrons can change, as they are swapped and shared as it interacts with other atoms, making chemical bonds, but carbon “likes” to have six of its own to balance the electric charge of its protons, and “likes” to share with other atoms to make a total of twelve.
If you try to break down an electron, you’re not going to have much luck. Electrons are fundamental They belong to a family of particles called leptons.
If you turn your attention to the protons and neutrons, you will find they are made of other particles, called quarks.
There are six different types of quarks: up, down, charm, strange, top and bottom. Protons are made of two up quarks and a down, and neutrons are made of two downs and an up.
Quarks are a bit funny: they never exist alone. They always hang out with either two other quarks, or with an antiquark.
… But now we’re talking antimatter, and that’s a whole ‘nother game.