Uno (stylized on usual branding as all capitalized) is an American card game that was made by Merle Robbins in 1971. It has since been bought by a company named Mattel. It uses 108 special cards that are made just to play Uno. It is similar to Crazy Eights.
The cards are put into 4 different groups: Red cards, green cards, blue cards and yellow cards. There are also some other cards called "Special Cards". Skip, Reverse, Draw +2(This card can be canceled by Reverse card which changes the way), Wild, and Wild +4 cards allow you to do something you cannot normally do, such as pick up two more cards.