Either by compiling a list for them or producing a guide for their task the purpose is to assist people in menial tasks that they don't have the time to do, or simply cant be bothered to do and would rather pay out a little bit for someone to do it for them.
At the moment, it's only £2.50 per task so it's pettance to pay for a virtual assistant and frees you up to do more important things like Facebook...