Generally "work" is what you do, your tasks. "Job" is a particular type of work. Also "job" is countable, "work" is uncountable except some specific contextual situations.

I have work to do (I am busy). I have a good job (I am successful) My work is difficult (The work I do at my job is difficult) They can also be used in the same way: Good job! Good work! My work as a teacher is fun. My teaching job is fun. My job as a teacher is to allow students to learn for themselves. My work as a teacher is based on allowing students to learn for themselves. Do your job! Get to work! What kind of work do you do? -- I'm a doctor. Do you have a job? -- Yes, I'm a doctor. A doctor usually does not say "JOB" because "Job" is more common work. A doctor has a CAREER because a career is more important work.