Electrons have a negative charge. The charge on an electron in an atom is the same size as the positive charge of the proton in the same atom. Protons have a positive charge.
The opposite charges of protons and electrons is what causes them to be attracted to each other. Electrons are not in the nucleus of an atom, but orbit it. There is the same number of electrons orbiting the nucleus as there are protons inside it. Electrons are the smallest part of an atom and are in constant motion. Atomic bonds are formed by either sharing or transferring electrons.