In Sweden, people celebrate their name days in addition to their birthdays. Your name day is the day of the year that corresponds to the name you were given at birth.
For example, if your name is Johan, your name day would be on June 24th because that is the day of the year when the saint John the Baptist is celebrated in the Swedish calendar, and Johan comes from John.
On your name day, people may congratulate you, give you gifts or cards, or invite you over for fika (coffee and pastries). It's kind of like having a second birthday celebration!
Some people take their name days more seriously than others, and it's not an official public holiday, but it's a fun tradition that has been around for a long time in Sweden.