All matters are made up of atoms which consist of electrons orbiting a nucleus (containing protons and neutrons).
When an object is neutral, it means there are equal number of negatively charged electrons and positive charges.
When an object is positively charged, it means there are more positive charges than electrons.
When an object is negatively charged, it means there are more electrons than positive charges.
Note that only electrons can be transferred to make the object become charged. Positive charges do not move!
Only two types of electric charges
SI Unit: coulombs, C
Note that one electron is not 1C. An electron has 1.6 * 10-19 C of charge. We need 6.25 * 1018 electrons to make up 1 C!
Law of electrostatic
Like charges repel, unlike charges attract.