Just what exactly do they do?
What they do.
Human Resources are in charge of making sure employee's are working within their rights, to ensure they're getting the right pay, the right hours and working in the right conditions. If an employee has a certain issue they'd like resoled regarding their workplace then they'll most likely consult their employer, if this proves to be in vein then Human resources will be contacted. Human Resources will either assure the employee that this 'issue' isn't acctually an issue at all if that is the case or if that isn't the case and there is a problem that could be potentially threatening or is violating the employee's rights then they'll take action.
Human Resources can offer employee's contracts to have proof that this employee has agreed to this payment in exchange for their work or to make sure they agree to certain hours (aslong as these wages and hours are within the legal limit) They have to take into account people's information when they're issuing someone a workplace, they look at their history, their medical information such as allergies and if a workplace breaches such medical condition then Human resources will take action against the employer and the employee who breached these margins. If there is an allergy to a certain food in the workplace that food will be banned from the workplace as it can be life threatening and therefore breaching employee's rights.