The first sentence is just a normal sentence. The second case is a use of *to do* as an auxiliary verb for [emotive emphasis][1], in an affirmative sentence.


> We do not normally use do or does in affirmative sentences, Ali, but
> we can use them for emotive or contrastive emphasis when we feel
> strongly about something:
> 
> *She thinks he doesn't love her, but he **does** love her. He really does!<br>
> You **do** look pretty in that new outfit! Quite stunning!<br> Are you all
> right? You **do** look a bit pale.<br>**Do** please sit down.<br>I don't see very
> much of my old friends now, but I **do** still email them.<br>Was that a
> joke? I **do** believe you're teasing me!*

So, the difference between the sentences is the second sentence places emphasis on the verb *to work*.

  [1]: http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv298.shtml