Laetare is the ancient name for the fourth Sunday in Lent. It means rejoice.
The introit for Laetare Sunday:
Rejoice, O Jerusalem: and come together all you that love her: rejoice with joy, you that have been in sorrow: that you may exult, and be filled from the breasts of your consolation. Psalm: I rejoiced when they said to me: "we shall go into God's House!" The texts of the antiphon come from Isaiah 66:10-11 and Psalm 122:1. I could listen to that all day....and maybe I will. ;-)