What is Valentine's Day? Valentine's Day is a holiday that's popularly observed as a day to celebrate love, especially by those in romantic relationships. Valentine's Day is traditionally observed by exchanging gifts or cards called valentines. A valentine is a sweetheart: specifically, someone who receives a greeting or attention on Valentine's Day. ... Asking "Will you be my valentine?" is like asking "Will you go out with me?" and saying "I like you." Sending a card is a common way to let someone know you want to be their valentine. Valentine's Day is named after Saint Valentine, a Catholic priest who lived in Rome in the 3rd Century. So how are you celebrating?