A career is a course of successive situations that make up some activity. One can have a sporting career or a musical career, but most frequently "career" in the 21st century references a workinging existence: the series of jobs or positions by which one earns one's bread.
In the relatively static societies before modernism, many workers would often inherit or take up a single lifelong position (a place or role) in the workforce, and the concept an unfolding career had little or no meaning. With the spread during the Enlightenment of the idea of progress and of the habits of individualist self-betterment, careers became possible, if not expected.
By the late 20th century a plethora of choices (especially in the range of potential occupations) and more widespread education had allowed it to become fashionable to plan (or design) a career: in this respect the careers of the career counsellor and of the career advisor have grown up.
For a pre-modernist "career" structure, compare cursus honorum.
See also: career development, career management