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!
You do look pretty in that new outfit! Quite stunning!
Are you all right? You do look a bit pale.
Do please sit down.
I don't see very much of my old friends now, but I do still email them.
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

The first sentence is just a normal sentence. The second case is a use of to do as an auxiliary verb for emotive emphasis, 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!
You do look pretty in that new outfit! Quite stunning!
Are you all right? You do look a bit pale.
Do please sit down.
I don't see very much of my old friends now, but I do still email them.
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.

The second case is a use of to do as an auxiliary verb for emotive emphasis, 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!
You do look pretty in that new outfit! Quite stunning!
Are you all right? You do look a bit pale.
Do please sit down.
I don't see very much of my old friends now, but I do still email them.
Was that a joke? I do believe you're teasing me!

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!
You do look pretty in that new outfit! Quite stunning!
Are you all right? You do look a bit pale.
Do please sit down.
I don't see very much of my old friends now, but I do still email them.
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