What type of reaction is:

NH3(aq) + HBr(aq)
NH4Br(aq)

The reaction NH3(aq) + HBr(aq) → NH4Br(aq) is a double displacement reaction, also known as a precipitation reaction. In this reaction, the ammonium (NH4+) ion from NH3 combines with the bromide (Br-) ion from HBr to form ammonium bromide (NH4Br).