The Feast of All Saints is a holy day in both the Anglican and Catholic churches (as well as several other denominations), celebrated annually on November 1. It is a day dedicated to all the saints of the Church, that is, all those who have attained heaven. Over the centuries, many of these saints have suffered and even died for Our Lord, sustained in life largely by their tenacious faith.
Although millions—or even billions—of people may already be saints, many All Saints' Day observances tend to focus on known saints, those recognized in the canon of the saints by the Church.
The liturgy for All Saints’ Day usually includes the well-known hymn, Bishop William W. How’s For all the saints. Ralph Vaughan Williams, who composed the music, gave it the title Sine Nomine (Latin for “Without A Name”). While it follows a Renaissance tradition of naming certain compositions "Sine Nomine" if they are not settings for preexisting tunes, it is an interesting title choice given that most of heaven’s saints are effectively nameless—known only to God.
Source: The Catholic Encyclopedia