Let me start this chapter with explaining the theory of superstrings. Basically, superstrings are tiny supersymmetric 1D "strings". This is different from the particle theory, in which everything is made out of tiny points, rather than strings. A string might look exactly like a particle; its mass, charge, and other properties are determined by how the string vibrates. The theory states that everything is made up of how these strings react with each other. 

Let me show you an example from Futurism, in an article about superstring theory: 

"A string's "vibrational mode" is only a fancy way of identifying the manner in which it oscillates. Here is a theoretical example: if a string vibrates (or wiggles) in one manner (a), it could exhibit characteristics of an "up" quark. If a second string is introduced with the same properties, we now have two (a-vibrational) strings, or basically two "up" quarks. However, when a third string that acts in a rather different manner (b), acts as a "down" quark, the result interaction simplifies as (a+a+b) or two up quarks and one down quark. The result of two up quarks and one down quark produces a proton." -Donavan Mason, author of the article The Physics of Everything: Understanding Superstring Theory. 

I suggest you go check it out- it would probably explain everything better than I could! (I'm just a wimpy little middle schooler)!

Donavan later went on to explain that one should not think about the + in (a+a+b) only as a mathematical sign, but also as interactions between the quarks, resulting in a string/particle itself. So, you can think of (a+a+b) as a string! Later in the paragraph it was added that string theorists call these gluons (g). Gluons are like the glue that bind these together.

You might be wondering what a quark is. Quarks are elementary particles, meaning it is unknown whether they are made up of yet smaller particles. They combine to form hadrons, which make up atomic nuclei. Interesting enough, quarks are never found alone. Most of what we know about them is from studying hadrons. 

Another thing I should also explain is supersymmetry. Supersymmetry is a type of spacetime symmetry in which two basic classes of elementary particles: bosons, which have an integer based spin, and fermions, which have a half integer spin. Each particle from one group has a partner the other, called a superpartner. Their spins differ by a single half integer. In "unbroken" supersymmetry, each superpartner would be almost exactly the same (in mass and internal quantum numbers) except the spin. "Broken" supersymmetry would have the superpartners with different masses. So far, no superpartners have been observed with modern equipment. 

Back to superstrings, in traditional superstring theory, there are two types, open and closed. Open strings have endpoints that may very in length, and closed strings are circular (unless they are vibrating, then they can be described as wiggly XD), and don't really have any endpoints. Only some string theories have open strings, but all require closed strings. 

So, to sum up this chapter, superstring theory states that every particle is made out of different vibrational modes and interactions between different strings.