person or company that employs workers
An employer is a person or institution that hires employees. Employers offer wages or a salary to the workers in exchange for the worker's work or labor.
One speaks of wages if the employee is paid by the hour and of salary if he is paid a set rate per pay period. Wages are paid for all hours worked, including overtime, but a salary is typically not paid more for more hours worked than the minimum.
Employers include everything from individuals hiring a babysitter to governments and businesses which may hire many thousands of employees. In most western societies governments are the largest single employers, but most of the work force is employed in small and medium businesses in the private sector.