The difference between (aq) and (l) in chemical equations is in the state of the substance being represented.
(aq) stands for "aqueous," which means that the substance is dissolved in water, resulting in an aqueous solution. In the equation you provided, HCl(aq) and NaOH(aq) represent aqueous solutions of hydrochloric acid and sodium hydroxide, respectively. This means that these substances are dissolved in water to form a solution. Aqueous solutions are typically indicated by the presence of water (H2O) as the solvent and are often used in chemical reactions.
On the other hand, (l) stands for "liquid," indicating that the substance is a pure liquid state. In the given equation, H2O(l) represents pure water, which is the product of the reaction between HCl(aq) and NaOH(aq). The (l) is used to differentiate water as a distinct liquid product in this equation.
So, to summarize, (aq) indicates that a substance is dissolved in water to form an aqueous solution, while (l) represents a pure liquid state.