That desk in front of you and everything else around you is made up of atoms. An atom consists of electrons orbiting around a nucleus. An atom is increadibly tiny. You could line up 10 million of them inside a millimeter. What if we could scale up an atom so that the nucleus was the size of a basketball? The orbits of its electrons would then be 15 miles away.
From this you can understand that atoms are almost all empty space. The nucleus of the atom is composed of quarks. If you could see a quark or an electron up close, it might appear as a tiny vibrating glow of energy. It turns out this world, which is causing us so many problems and so much stress, is mostly an illusion!
The electrons orbit the nucleus at about the speed of light. If you could see them, they might appear as a blur. They do not orbit in a plane like the pictures in books. They create a shell. Sometimes two or more atoms will share electrons, causing them to link together forming a molecule.
Looking at that desk in front of you again, it looks pretty solid. Actually, unless your desk is floating in deep space where the temperature is close to absolute zero, the molecules of your desk are vibrating like crazy. Picture the molecules bouncing around and smacking into each other like balls on a pool table.
