When a person decides to voluntarily leave their job or they reach the age of 60, in which case the government relieves them from working as full time paid employees, such persons are said to be retired. In other cases, one may not be able to work as much because they have grown older, so they choose to retire from work. A voluntary retirement is usually taken when one is confident of their finances and has enough money saved or invested to help them lead a comfortable life without actively working.
Example:
The Government of India asks its employees to retire by the age of 60, offering them a sum of money as pension, after they retire to help them take care of their day to day needs.