A name day is the day of celebration in lieu of, or in addition to, a birthday, held on the day of the saint who shares one's name.
Name days are rarely celebrated in English-speaking cultures, but are common in many Eastern Orthodox countries, such as Greece, some Roman Catholic countries, such as Poland, and a few Protestant countries, such as Sweden.
In these countries, all those persons having a particular Saint's name rejoice on the same day. Observing your name-day is considered to be spiritually important.