http://www.bbc.com/news/uk-politics-32810887 By Brian Wheeler & Alex HuntBBC News 2 June 2016 From the sectionUK Politics Image copyrightREUTERS What is happening? A referendum is being held on Thursday, 23 June to decide whether Britain should leave or remain in the European Union. This article is designed to be an easy-to-understand guide - if you have any questions you can send them in using this link. We'll be answering a selection at the bottom of the page. What is a referendum? A referendum is basically a vote in which everyone (or nearly everyone) of voting age can take part, normally giving a "Yes" or "No" answer to a question. Whichever side gets more than half of all votes cast is considered to have won. Why is a referendum being held? Prime Minister David Cameron promised to hold one if he won the 2015 general election, in response to growing calls from his own Conservative MPs and the UK Independence Party (UKIP), who argued that Britain had not had a say since 1975, when it voted to stay in the EU in a referendum. The EU has changed a lot since then, gaining more control over our daily lives, they argued. Mr Cameron said: "It is time for the British people to have their say. It is time to settle this European question in British politics." What is the European Union? The European Union - often known as the EU - is an economic and political partnership involving 28 European countries (click here if you want to see the full list). It began after World War Two to foster economic co-operation, with the idea that countries which trade together are more likely to avoid going to war with each other. It has since grown to become a "single market" allowing goods and people to move around, basically as if the member states were one country. It has its own currency, the euro, which is used by 19 of the member countries, its own parliament and it now sets rules in a wide range of areas - including on the environment, transport, consumer rights and even things like mobile phone charges. Click here for a beginners guide to how the EU works.