Molecules are made up atoms.
An atom is the smallest indivisible part of an element or compound and is made of particles called protons, electrons and neutrons.
A molecule is the smallest particle of an element or compound that bears the chemical properties of that element or compound. Molecules are composed of atoms of one or more elements. There are molecules which are made up of only type of atom. For example a molecule of oxygen is made up two oxygen atoms that have bonded together to form that molecule.
Some molecules are made of atoms from different elements. A molecule of sodium chloride, table salt, for example is made up of an atom from sodium and an atom from chlorine to form the molecule.