Ions refer to the state formed after atoms gain or lose electrons. Because electrons are negatively charged, if atoms gain electrons, they will form negatively charged ions, that is, negative ions (or anions), and after atoms lose their charges, they will be positively charged, that is, positive ions (or cations), that is, positive ions and negative ions.

In fact, the reason is the composition of atoms. Atoms consist of protons and electrons (mainly neutrons). Charged protons and electrons are positively and negatively charged respectively. In the atomic state, the number of protons and electrons are equal, so the atom has no charge. After losing electrons, the number of protons is greater than the number of electrons, that is, the positive charge is greater than the negative charge, so the formed ions are positively charged, which is called positive ions. Instead, atoms get electrons.