The UAW is a large trade union in the United States for people who work in the car industry — the workers who build cars and trucks in the factories, and in some other factories too. A trade union is a group workers join so they can bargain together with the company about pay, hours and safety, instead of each person arguing alone. The UAW became famous for organising the big factories in Detroit in the 1930s and for the strikes it has called since. When you read that 'the UAW went on strike', it means the union told its members to stop working until the company agreed to better terms. You say the three letters one by one: U-A-W, and you normally put 'the' in front of it. Note that the letters actually stand for United Automobile Workers (the full official name is longer: United Automobile, Aerospace and Agricultural Implement Workers of America). Some sources write it as 'Union of Automotive Workers', but the usual expansion you will see in American news is 'United Auto Workers'. The union has also taken in workers outside car factories over the years — university staff, for example — so the name is now wider than the membership it describes.