Second Coming
The Second Coming (sometimes called the Second Advent or the Parousia) is a Christian and Islamic belief regarding the future (or past) return of Jesus Christ after his ascension to heaven about two thousand years ago. The idea is based on messianic prophecies and is part of most Christian eschatologies.
Advent
The theme of readings and teachings during Advent is often the preparation for the Second Coming, while also commemorating the First Coming of Christ at Christmas. The first clear references in the Western Church to Advent occur in the Gelasian Sacramentary, which provides Advent Collects, Epistles, and Gospels for the five Sundays preceding Christmas and for the corresponding Wednesdays and Fridays. While the Sunday readings relate to the first coming of Jesus Christ as saviour as well as to his Second Coming as judge, traditions vary in the relative importance of penitence and expectation during the weeks in Advent.