HBr is a strong acid; completely dissociates in a water solution as H+ and Br-.
NH4 is a weak base. Dissociates as NH4+ and OH-.
Your products are H20 (l) and NH4BR (aq). the phases of the ions are impt.
I think this is mostly restricted to the arrhenius definition where acid has H+ and base has OH-. Consider a buffer, solution, and this won't be the case. Or consider this reaction with a weak acid and weak base
HF + NH3 <--> NH4+ + F-
The F- will further react with water but that's not relevant right now.