Let me try explaining string theory.
For those advocates of string theory, strings are believed by some to be the sub component parts comprising quarks- a subatomic particle– hence it might be the quark ultimate fundamental particle at least hypothetically.
String theory is quite possibly deceased, but funding dies hard, as do those scientists dependent upon it. If no new particles are discovered at the Large Hadron Collider, that may likely be the interpretation.
If SUSY -Supersymmetry goes- so too will superstring theory as one is a product of the other.
Let me digress a bit and talk about particles. Let’s start with the two main categories of elementary particles, Fermions and Bosons.
You, me, the chair, the ground I walk on, is composed of energy in a form that appears solid, we call matter. Matter is mostly made up of Fermions we recognize as atoms.
Atoms are made up of three main things; electrons also known as Leptons- nothing smaller yet known makes them up although there are some who believe they may be made up of two smaller parts- but not yet proven- and they come in different types.
– And protons and neutrons. Unlike electrons both protons and neutrons are known to be made up of smaller things. They are known as quarks. There are six varieties of quarks.
In simple parlance a proton is composed of 3 quarks. A neutron is also composed of 3 quarks but in a totally different configuration. As a result one has a positive charge and one is neutral. Their mass is about the same.
If strings exist, they might explain why quarks are different depending on how their internal string vibrates.
Think music notes here (although not music) but think different notes.
Characteristics would be different in different types of quarks because a string or strings inside vibrate differently– so contrast a deep bass note -low A- vs a high C note.
Photon energy works this way, so long wave red light does not pack the energy of short wavelength violet or ultra violet.
Many things in nature repeat in other examples. So perhaps if strings exist, this might be a layman’s explanation for quark variety.
Bosons are a second class of elementary particle, and are divided into two categories; Elementary such as photons and gluons, and Composite such as mesons.
If you have a magnet, the magnetic force lines are actually invisible photons. Photons carry the electromagnetic force. Gauge Bosons are force carriers. Some of those other forces hold the nucleus of an atom together (strong force) some are responsible for radioactive decay (weak force). If a graviton is ever discovered it may be the force that carries gravity.
It is the Higgs Boson that carries the force called the Higgs mechanism that gives energy the state we refer to as mass.
Here is a good source of explanation about particle physics.
Here is an excellent TED talk by Brian Greene, a Professor at Columbia University, on his views of why strings determine the existence of every particle and every force in the universe.
So strings may be what give tiny particles their characteristics, (or not). They in turn depending on natures recipe, determine how larger particles behave, and they in turn make up atoms. Atoms can make up molecules, which make up the world around us and our universe!