A job is a regular and official activity that you do, and receive money for your activity. It is also called a profession or an occupation. You can have a full-time job (40 hours a week) or a part-time job (around 25 hours a week).
The word job is a countable noun:
Right after graduating from college, I worked two jobs so that I could pay off my student loans faster.
Terry has had seven jobs in the past five years.
The word work is more general than "job" - whereas "job" is a specific occupation/profession, "work" refers to general efforts and activities done to accomplish a goal. "Work" can be done both inside an official job and outside a job!
The word work also refers to the context of your place of employment - so we
"I start work at 7 AM."
"I start my job at 7 AM"
"I finish / leave work at 4:30."
"I finish my job at 4:30"
- An informal way to say "leave work" is "get off work"
"We go to work by car."
"We go to our job by car"
"I went to the bar with some friends from work."
"I can't access Facebook when I'm at work." (not "at my job")
"Work" is an uncountable noun, so it cannot be plural:
I have three works to do this week.
I have three projects to do this week.
I have three things / tasks to do this week.
Your career is the total progression of your professional life. It can include many different jobs over the years. You can have a career in (a field) - for example, a career in politics / journalism / teaching / finance.