Very common question.
1. HR deals with recruiting and selection of employees for new positions or for positions left open after someone has left the company;
2. HR monitors training needs within the organization, prepares training plans, registers people to trainings, conducts trainings, assesses people for skills to see what trainings they need to develop to get promoted or to perform better;
3. HR prepares payroll (calculates salaries) and additional benefits of employees, monitoring all these at the same time;
4. HR prepares salary increase proposals and calculates scenarios to check if all these fit the given budget;
5. HR coordinates the performance evaluation process of all employees;
6. HR prepares satisfaction surveys within a company;
7. HR prepares reports containing various indicators that monitor the company's status like value of attrition (employees leaving the company), sickness rate, training hours/employee, employee satisfaction, etc;
8. HR creates work procedures for all employees to follow in order to have a standardized flow of information in the company;
9. HR prepares all employment documents like contracts, contract changes, job descriptions, etc.
10. HR monitors medical checks and employee health.
and many more...