Does Human Resources determine whether you get the job at most companies?

Not really. In most large companies, Human Resources plays a role in the hiring but the ultimate decision maker will be the hiring manager (usually the manager to whom the position would report or the department manager who has responsibility over the unit in which the candidate is applying). Human Resources receives resumes, screens candidates, is involved in the interview process and will play a role in the salary negotiations. They will also provide approval for the hiring ticket (if one is needed), provide general guidance in the hiring process and ensure that any hiring decisions are made equitably and fairly without descrimination, etc. When human resources screens candidates they may eliminate a candidate because he/she does not possess needed qualifications but usually the hiring decision is done by the responsible business manager. This is why, when applying for a job it's beneficial to try to discover who the hiring manager is and deliver your resume directly to that individual. Human Resources receives hundreds, sometimes thousands of resumes in a week and is sometimes a bit of a black hole. It's always best to try to find out who the hiring manager is and deal with that individual directly rather than through Human Resources. Even in companies where Human Resources has a lot of power, the hiring manager will still hold a lot of influence over who ultimately gets hired.