McDonald's In a chain of fast food restaurants.
The business started out as a Hot Dog stand set up by Richard and Maurice McDonald in 1937. Using the money they made from the stand they shut it down to open their first restaurant in 1940. After a while the brothers had realized that they made most of their money from hamburgers, they decided they could make more if that was all they sold. They shut down for a while, and when they reopened they sold hamburgers, Chips, milk shakes and very little else. The new format was extremely successful as they were able to sell burgers for 15c, scarcely half the price of other diners, by the early 1950’s the McDonalds brothers were franchising out this format to other people, however it is not considered that the modern McDonalds business started until the entire franchise business was bought out by one of the Franchisees Ray Croc in 1955.
Today McDonalds is the world's largest chain of fast food restaurants serving 54 Million Customers every day! They mainly sell Fries, hamburgers, cheeseburgers, chicken, breakfast items, soft drinks, desserts and milkshakes. More recently, it also offers salads and fruit products.
It’s not exactly healthy eating, too much of it makes you get really fat. In 2003 Morgan Spurlock heroically experimented on himself. For a month he ate only McDonald products. During this time his body mass increased. He suffered irreversible liver damage  and had unhealthy mood swings. Quite possibly he saved the lives of other diners who might be tempted to eat too much fast food. The documentary shows clearly why eating too much fast food is extremely unhealthy. Those Americans who eat exclusively fast food put their health and their lives at risk. See Super Size Me. More on Supersize Me. See also McLibel
Warning: Even if you make what you hope is a healthy choice and eat salad the sauce McDonald's put onto that salad is thoroughly unhealthy and worse that some standard McDonald's products. 
Critics may argue that the big M stands for murder as they kill a few customers with unhealthy food and additives.
McDonalds has become a byword for low paid drudgery jobs working antisocial hours. They are known as an anti union company.
Mc or Mac
They took out a court case against a Scottish rival MacDonalds arguing in a Scottish Court that Mc and Mac are essentially the same. Unfortunately people were too polite to ban them from calling themselves either Mc or Mac in Scotland.