£ is the Great British Pound (GBP), also known as the Pound Sterling or Sterling. Used in the UK. NOT to be confused with the €.
€ is the Euro, used in the Eurozone. Not to be confused with the £. Note that not all EU countries use the Euro (The eurozone currently consists of: Austria, Belgium, Cyprus, Estonia, Finland, France,Germany, Greece, Ireland, Italy, Latvia, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia, and Spain)
$ is the US Dollar (USD). Used in the USA
The EU countries are: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, United Kingdom. If you buy from any of these countries and you are outside the EU you do NOT pay VAT but you DO pay customs and import duties if your parcel is checked and the contents and value are liable for tax. If you live in any of these countries and buy from another one of these countries, you DO pay VAT, at the local rate of the country from which you are buying but you do NOT pay customs or import duties in your own country.
The EEA countries are the above + Norway, Iceland and Lichtenstein
The EFTA countries are the above + Switzerland
If you need to convert currency you can use Google. Just type the amount and the two currencies. I tend to type 50 gbp to usd, for example
Or you can use a currency converter such as XE.com