Career has various meanings, mostly having to do with a job.
The word comes from a French word meaning "road". It came to mean someone's path through life, or through a particular part of life, for example one's time in school. Later many people used the word only for someone's work and, later yet, a profession, or a job that has an opportunity for advancement. Alternatively, "a career" often means a sequence of related jobs within a single industry or sector, such as "a career in medicine" or "a career in the building trade".