In general, the word job refers to an activity of economic production. In this sense, a group may divide up a set of tasks among its members, each task being "the job" of the individual it is assigned to.
However, in capitalist societies, the word "job" has become synonymous with "employment". This refers to the long term relationship between a laborer and those who have legal control of the other factors of production. In this sense, laborers talk of "getting a job", or "having a job". This conception of a "job" as a possession has lead to its use in (possibly self-consciously) absurd slogans such as "money for jobs, not bombs".
See also Profession.