It's a grammatical difference.

As Aegis says, the word 'job' is countable. This means that:

* It has a plural form - jobs

* You use 'many' and 'few'

* You need to put 'a' or 'one' before it in the singular

The word 'work' is uncountable. This means that:

*  It has no plural form

*  You use 'much' and 'little'

*  You can't put 'a' or 'one' before it.

He's looking for a job.

He's looking for work.

Are there many jobs here?

Is there much work here?

Sometimes nothing. Like in the sentences:

"Good job!"

"Good work!"

But you can't always swap them out because <em>job</em> is countable, and <em>work</em> isn't.

thank you both of you .i guess you're right 

NB Your question should be 'What is the difference between work and job?'