What happens to the composition of an atom to cause it to become positively or negatively charged? keep it simple

An atom is neutral when the number protons and electrons are equal, so when either of these two are taken away or added it will change the charge of an atom. If protons are added or electrons are taken away, a once neutral object will be positive. But if protons are taken away or electrons are added to a once neutral atom, the charge will become negative. Usually electrons are the ones that move and change the atoms charge.