VAT is Value Added Tax levied on sales, currently rated at 20% in the UK; it applies to most goods and services sold in the EU.

Click for more information direct from HM Revenue & Customs.
 

It may be possible for you to reclaim the tax, or for us to sell to you without VAT, if you are from overseas and either you or we are immediately exporting the goods outside the EU. If there's any doubt at all, we have to add VAT and leave it up to you to reclaim the charge from Revenue & Customs.

Here's the link to find out more: HM Revenue & Customs Notice 703.