Molarity:This is a measure of concentration in terms of moles per liter, like measuring ingredients for cookies in cups per batch.
Limiting Reactant:This is the ingredient that runs out first during a chemical reaction - just as if you run out of flour while making cookies, it limits how many batches you can make.
Excess Reactant:An ingredient that remains after all other reactants have been used up - like having leftover chocolate chips after all your cookie dough has been baked into cookies.