Both 帮(bāng)助(zhù) and 帮(bāng)忙(máng) means ‘help’ while they are distinct in verbal structure.
帮(bāng)助(zhù) can be used in the structure ‘V+O’ such as bāngzhù-biérén 帮助别人 ‘help others’, but帮(bāng)忙(máng) is in the form of ‘帮(bāng)+O+忙(máng)’ such as bang-biérénde-máng 帮别人的忙 ‘do somebody a favor’.