A person's job is their role in society. A job is an activity, often regular and often performed in exchange for payment. Many people have multiple jobs, such as those of parent, homemaker, and employee. A person can begin a job by becoming an employee, volunteering, starting a business, or becoming a parent. The duration of a job may range from an hour (in the case of odd jobs) to a lifetime (in the case of some judges). The activity that requires a person's mental or physical effort is work (as in "a day's work"). If a person is trained for a certain type of job, they may have a profession. The series of jobs a person holds in their life is their career.
Jobs for people
Most people spend up to forty or more hours each week in paid employment. Some exceptions are children, those who are retired, and people with certain types of disability, but within these groups many will work part-time or occasionally, will work in one or more volunteer positions, or will work as a homemaker. From the age of 5 or so, many children's primary role in society—and therefore their 'job' -- is to learn and study as a student.