A greeting card is a folded card, illustrated, usually depicting expressions of friendship or other feelings, with a blank space for the sender to add a signature or handwritten message. Greeting cards are usually given on special occasions, birthdays, and other holidays, but are also designed to convey thanks or other sentiment. Greeting cards are packaged with an envelope, and come in a variety of styles, from standard, to personalised, to pop-up and musical. There are both mass-produced as well as handmade, distributed by hundreds of companies large and small, the most prominent being Hallmark worldwide. Greeting cards are inexpensive.