The "Te Deum" is a Christian hymn. Its original text was in Latin. It is named after the first few words, "Te Deum laudamus" (We praise thee, O Lord). It was probably written around the 4th or 5th century. Most say that either Augustine of Hippo or Ambrose wrote it. Some say it was by Nicetas, bishop of Remesiana. Others have said that the hymn was taken from two (or more) earlier hymns: one to God the Father and another to God the Son. After this idea, the second hymn begins with the phrase "Tu rex gloriae, Christe". The petitions at the end of the hymn (beginning "Salvum fac populum tuum") are from verses from the book of Psalms, added to the original hymn later on.
Te Deum is close in theology to the Apostles' Creed. It has both a poetic view of the heavenly liturgy with a declaration of faith. "God" is named from the start of the song. The hymn then names all people who praise and respect God, from the hierarchy of heavenly creatures, to Christians who are already in heaven, to the Church in all the world.
Te Deum then returns to its creedal formula, singing about Christ and remembering His birth, suffering, and glorification. Then the hymn stops singing about praise, both the Church in general and the singer himself, and asks for mercy on past sins, protection from future sin, and the hope to be reunited with Christians in Heaven.