What is "feast of orthodoxy"

The Feast of Orthodoxy (also knowns as the Sunday of Orthodoxy or the Triumph of Orthodoxy) is celebrated on the first Sunday of Great Lent (six Sundays before Pascha) in the liturgical calendar of the Eastern Orthodox Church and Eastern Catholic Church (Eastern Catholics of Byzantine rite). The Feast is kept in memory of the final defeat of Iconoclasm and the restoration of the icons to the churches.