A career is often considered to be the work you do during your life. For example a teacher, nurse or pilot. But what if someone is a teacher for 10 years, then becomes a pilot for a couple of years and then starts their own business running a pilot training college? They are said to have changed their career three times. But although they have had three very different jobs, they are still said to have a single career.
So your career can refer to any number of jobs and things you do to earn a living. In fact your career is best regarded as a journey, starting with your first job and continuing until you retire.
So a more accurate description of a career might be all those things you do that lead to any type of work or employment during your life.
And guess what this means - you've already started on your career journey! Many of the skills and learning you do at school will be used in your work someday. And you may already have preferences for certain types of subjects and skills (for example, science, business or art) which will incline you towards certain types of work in the future.