To start with the EU was designed to help peace in Europe by increasing trade between countries.
As trade created wealth a big aim started to share it out more fairly. The richer areas were expected to pay money to the EU which would be used to help poorer areas.
The map below shows wealth across the EU.
Money or how much it costs us to be in the EU is probably the biggest discussion point on membership in the referendum.
The UK is one of 10 member states who pay more into the EU budget than they get out, only France and Germany contribute more.
The National Audit Office worked out the cost to the UK in 2014 was £5.7bn which if you divided it by 365 would give you a value of close to £15.6 million a day.
The map mirrors the wealth map but it shows areas which receive money or aid from the EU.
Large parts of North, West Wales and The Valleys receive the highest levels because they earn less than 75% of average EU income.
Wales will have been given over £5 billion of EU money by 2020.
Wales gets far more money from the EU than it pays in.
In the EU there are strict rules about both of these in The Common Agricultural Policy (CAP) and The Common Fisheries Policy.
Approximately 40% of the EU budget goes to farmers in terms of payments sometimes called subsidies.
Many farmers and farming unions want to stay in the EU (but not all) because EU payments can make up more than half of a farmers income.
Wales and the UK have some of the best fisheries in the EU but fishing industries are getting smaller.
There is a big argument as to whether EU rules are helping to protect supplies of fish for the future.
Most people in the UK agree that allowing free access to all EU boats to fish in British waters is bad for the UK fishing industry.
The United Kingdom still has control of its borders and everyone from everywhere has to show their passport and is checked.
Citizens of EU member countries have the right to live and work in any EU country.
Many millions of ‘Brits’ live and work across Europe but many citizens of other European countries also move here.
Some say this is good as people from the EU bring essential skills and are more likely to work than UK citizens so they pay more in taxes than they take out in services.
Some say it is bad because migrants compete for jobs, housing and use services.
Rules and regulations are sometimes called ‘red tape’ opponents of the EU say it is bad because it costs business extra money.
People in favour of the EU say it is good because the rules and regulations are mainly to give workers employment rights such as stopping them being forced to work too long, to protect consumers when they buy things and to protect the environment.
Trade is the main way that a country earns money.
The rest of the EU is our biggest trading partner and thanks to the EU that trade is free from most charges.
Supporters of the EU point out that EU member states have trade agreements in place with nearly every country in the world.
In addition the EU has been agreeing a big deal with the United States will create the biggest free trade area the world has ever seen.
Quitting the EU would mean the UK would not be part of the new deal with the USA.
Opponents of remaining in the EU believe that if the UK left the EU then it would be free to agree its own new trade deals which might be better than those already agreed by the EU.
Unless we vote leave we would not know if we could negotiate such deals quickly enough; or if we could be stuck not being able to trade freely with most of our main markets.
These are just some of the main thins to think about; many others exist such as:
Just about anything that you can think about is affected by our membership of the EU.
After reading all three articles and carrying out the activities. Use the accompanying A3 sheet to help you to carry out an investigation into the 2016 EU Referendum in Wales.
Another issue you may find of interest, Investigating The Welsh Government Elections 2016.