whats ESTA?

[Disfan]

Apart from esta being my aunts friend, what is it and where how do I do it if I even need to do it?

[Slowhand]

It is the new system of vetting travellers to the US and will eventually replace the green visa waiver forms that you have to fill out every time you travel to the US from the UK.
Registering is very simple and details can be found here. You get an instant response if you are successful and you are given a reference number which is valid for 2 years or so.
I registered only the other day and found the process very easy to do on line.
Having said that the system is not fully up and running yet as apparently you still need to fill out the visa waiver forms as before.

[Skywatcher]

That said I would still fill out the ESTA forms before you go