All chemical reactions are at the "atomic level." In order for a chemical reaction to occur atoms must collide with a combined energy equal to or greater than the activation energy.
Molecular, ionic and net ionic equations are merely three different ways of representing the same thing: a chemical reaction where atoms are interacting (usually in aqueous solution).
The net ionic equation is handy because it deals with only the specific particles which are reacting, and omits the particles which aren't, called "spectator ions." Obviously, from the name, these particles are ions. The ionic equation shows the individual ions and sometimes molecules which are involved in a reaction. It may include "spectator ions." The "molecular equation" treats everything in the reaction as if it were a molecule whether it actually is or isn't.
HCl(aq) + NaHCO3(aq) --> NaCl(aq) + CO2(g) + H2O(l) .... "molecular equation"
Neither HCl, NaHCO3, nor NaCl exist as molecules in this reaction. They are dissolved in water and exist as the component ions. Only CO2 and H2O are molecules.
H+ + Cl- + Na+ + HCO3^- --> Na+ + Cl- + CO2(g) + H2O(l) ... ionic equation
Everything which exists as an ion is written as an ion. This gives a clearer picture of how the particles actually exist.
H+ + HCO3^- --> CO2(g) + H2O(l) ..... net ionic equation
Shows only the ions which react and the corresponding products. It omits the spectator ions which don't take part in the reaction.
Note: It is a good idea to include the state symbols, particularly in the "molecular equation." In the ionic and net ionic equations it is understood that the ions are in solution and so the (aq) state symbol is omitted for ions.