what are anions and cations

A cation is a positively charged atom or group of atoms. e.g. H⁺,Na⁺, Fe³⁺,Mg²⁺,NH₄⁺,H₃O⁺etc..

An anion is a negatively charged atom or group of atoms. e.g. F^-,O^2-,SO₄^2-etc..