A hiring manager is the person the potential new recruit will report to in the workplace. This person is responsible for filling any vacant positions in their team. So, the successful candidate will end up working under the hiring manager in the same department.
HR teams work with hiring managers to help them find the right person for the available role. The main goal of both parties is to ensure that the successful applicant chosen is the one with the most relevant skills and qualifications for the job. Usually, the hiring manager will write the job description while HR will advertise the role.