“job” is the colloquial word for “employment”, or 'professional activity'.A job is a sum of duties that someone performs when working for an amount of money.
Of course, you could choose not to have a job, and try to subsist by yourself. But the society wants you to be part of the worldwide production process, as one job is a cog in the “society” wheel.

Indeed, the division of labor is at the basis of our society.
In other words, and to simplify, considering that men are not of equal “capacity” and have an interest in trading and in anything that could improve their standards of living, the many tasks (in science, industry....) required to fulfill human needs have been distributed among the global population as paid “jobs”.

Ah, money, money, money... Jobs are not all of equal values: when you farm, your activity allows you at least to subsist. Cleaning desks for a company won't help you living for long if you have no financial compensation. That is why our society is based on a monetary system: The money paid for a job allows you to have a share of the worldwide productivity: money entitles you to buy a diversity of goods, not necessarily reflecting your job.

A job is an important thing in an person's life: an average of 40 years in someone's life is dedicated to work. School, high school, colleges, universities promote jobs as the only way for adults to survive. When they graduate, students really begin to be skilled for a specific job. Human nature is well done: everybody has different tastes and skills. Imagine what would happened if everyone wanted to become an air pilot...

In a company, you can either be an employer, or an employee. But that's two flips of the same coin: when you're an employee, your job is secured by a labor standards code, and you are paid by your employer. When you're an employer, your job is also to pay yourself from the fruits of your company's benefits.

What's the best job on earth? Well nobody can't tell, except the owners of this Australian's island, who advertised in 2008 for “the best job on earth”: a worldwide contest was launched for these Australians to choose among participants the next concierge of the island!!