Protons and neutrons are made up of tiny particles called quarks.
A proton is a baryon made up two Up and one Down quark.
A neutron is made of two Down quarks and one Up quark.
The Up quarks possess a 2/3 positive charge while the Down quark possess a 1/3 negative charge.
When we refer that a proton consists of two Up quarks and a Down, this simply means that its net appearance matches this description.
It is thought that quarks themselves are surrounded by gluons.
Gluons are the basic particles underlying the strong interaction between protons and neutrons in the nucleus.