Bitcoin is a digital currency which you can use to buy goods/services.
Unlike Great British Pounds (£) and the US Dollar ($) it is not issued by any government, bank or treasury. Insead it is created by a process called ‘mining’ which requires high end specialist equipment and access to low cost electricity to be profitable. Most people now obtain bitcoin by exchanging conventional fiat currency (£ or $) for bitcoin using an online exchange. There are many services and exchanges which offer slightly different rates and features but your main concern should be security. For information on how to buy bitcoin safely see How to buy Bitcoin
Once you have some Bitcoin you should follow our guidance on how to use Secure Storage to keep everything safe.