Card Reading Day is celebrated on February 21, 2017. The day is a chance for sentimental people to get their saved cards out for reading them. A greeting card is an illustrated, folded card featuring an expression of friendship or other sentiment.
Although greeting cards are usually given on special occasions such as birthdays, Christmas or other holidays, they are also sent to convey thanks or express other feeling. Postcards, which are single-sided without the fold, can function in a manner somewhat similar to greeting cards.
Greeting cards, usually packaged with an envelope, come in a variety of styles. There are both mass-produced as well as handmade versions that are distributed by hundreds of companies large and small. (With material from: Wikipedia)