REF: Physics Textbook Chapter 10, Electricity; Section 10.2, Atomic Structure and Electric Charge
All forms of matter are made up of atoms. A human body consists of about a billion billion billion (1027) atoms, which means they are much too small to be seen with even the most sensitive light microscope. But in recent years electron microscopes have been developed that can display individual atoms in a photograph (as seen in a photo of a gold crystal).
But no microscope is as yet capable of showing an atom's internal structure. For an understanding of the internal structure, we depend 
on indirect evidence that lets us develop models for the atom - representations that help us visualize it in terms of more familiar concepts. A model can help to do that, even if it isn't entirely correct.
It's well known that each atom has a nucleus made up of neutrons and protons at the center, with electrons orbiting about this nucleus (pictured). This representation is called a planetary model because of its similarity to the planets and sun of our solar system. This is a simple model to help give us a mental image of the atom; but to describe it more correctly, a discussion in Quantum Mechanics is required.
Aside from the need for Quantum Mechanics, there is another very misleading aspect of pictures like this often-used model. The relative size of the nucleus is greatly exaggerated. If we draw the atom to scale, with the nucleus the size shown in this figure, the electron orbits would be about a quarter-mile in diameter. The atom is almost all 'empty' space. (About the same proportion of 'empty' space as in our solar system). At least 99.95% of the mass of the atom is contained within its tiny nucleus.
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Atoms differ greatly in complexity. The simplest one is the hydrogen atom whose nucleus of one proton has one electron in orbit around it. But atoms that exist in nature range in complexity on up to the uranium atom with 92 electrons orbiting a nucleus of 92 protons and 146 neutrons.
Electric Charge
A quantity called 'electric charge' exists on every electron and every proton. First, charge exists in two types that, following the terminology used by Benjamin Franklin, are called 'positive' and 'negative'. Positive charge is held by the proton and negative charge is held by the electron. The amount of charge on the electron is exactly equal to the amount of charge on the proton. The neutron has no net charge, so it is electrically neutral.
The equal amounts of positive and negative charge balance each other. Since an atom in its normal state has the same number of protons and electrons, the total charge of such an atom is zero. As a whole, the atom is electrically neutral. A hydrogen atom, for example; with one proton and one electron has no net charge. If a neutral atom gains or loses an electron, it becomes negatively or positively charged. Such an atom, that is charged, is called an ion.
Ordinary-sized objects contain many atoms and therefore, many electrons and protons. When the total number of electrons and protons in an object is equal, the object is electrically neutral. We then say that such an object is uncharged, although what we mean is that it has the same amount of negative as positive charge. Because the charge on any object is made up of individual electron and proton charges, the total charge must be some whole number times the charge of the electron. In other words, charge is quantized - it exists in discrete bundles. These bundles are so small that, for ordinary purposes, the charge seems to be able to take any value.
We usually use the symbol q (or Q) for charge and measure it in a unit called coulomb (C), named in honor of Charles Augustin de Coulomb, an eighteenth-century pioneer experimenter on electric charges. The size of the coulomb is such that it takes 6.25 x 1018 electrons to give a charge of 1 C. Turning this around, the amount of charge on the electron (or proton) is 1.60 x 10-19 C. This amount of charge is very special in that it is the smallest quantity of charge know to exist on any object.* Physicists give this amount of charge its own symbol - the letter e.
Normally, a human body is electrically neutral, and contains about 1028 electrons and protons. If you were to lose one electron out of every billion, you would have a net charge of a few coulombs.
Experiments show that the net amount of charge in any region where no charge enters or leaves remains constant. That is, no net charge can be created or destroyed; if a net positive charge appears in one place, a net negative charge must appear in another so that the total amount of charge does not change. This is a statement of the principle of conservation of charge, a law of physics just as fundamental as the energy and momentum conservation principles.
*Currently popular theories propose that particles such as protons and neutrons are made up of more elementary particles called quarks which can have a charge of either + or - 1/3 or + or - 2/3 that of the electron. Some experiments have given evidence for quarks but no one has yet observed individual quarks.
Forces between Charges
Another important property of electric charge is that any two charges exert a force on each other. If both charges are are positive or both negative, then the force between them is repulsive - they push on each other. 
If one charge is positive and the other negative, the force is attractive (they pull on each other). In the picture, like charges experience a force (F) repelling them from each other. Unlike charges experience a force of attraction.
The force of attraction between the positive charge on the protons and the negative charge on the electrons holds the electrons in orbit around the nucleus of each atom. Then atoms combine with each other to form molecules, the charges in the atoms rearrange themselves so that electrical forces hold the molecule together. The atoms or molecules that make up a solid are held in place by electrical forces. The charges arrange themselves so that when you try to pull the solid apart, the forces of attraction between unlike charges dominate, and the solid is held together. When you try to compress the solid, the forces between like charges dominate and prevent you from compressing it. There is some flexibility in each direction and, if the applied force is strong enough, it can overcome these electrical forces holding the solid together, and either break or crush it.
The situation just described means that, aside from the gravitational force attracting you toward the earth*, every force that you experience directly is electrical in nature. (Gravitational forces from other bodies act on you, but are so weak as to be negligible.)
*Most of this content was taken from an older Physics textbook but current experimental theories about gravitation suggest a strong relation to electrodynamics and electromagnetism, so I take exception to the statement marked by the asterisk.
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