It's basically a summary of yourself and a chance to big your self up. What I find useful, is write down all the qualities they want for the job. For example, good team player, good organisational skills blah blah blah.
Once you have these write a summary about yourself, whilst incuding things you have done in the past (state examples) that prove you have these skills. Also include any lessons learned.
Festar: You can't plead poverty with 2 cars. That's like a little Kenyan chap pleading poverty with 2 packets of uncle bens rice hidden under his bed.