This Sunday marks the mid-point of Lent. “Refreshment Sunday” is a day when the discipline of Lent is relaxed for the day. Rose vestments may be worn (and will be at St. John’s). The Sunday is known as “Laetare” from the first words, Laetare Jerusalem, Rejoice, O Jerusalem, of the introit (introductory verse of scripture) in the Latin Mass.
It's not clear how “Mothering Sunday” came about, it is separate from the American introduction of “Mothers’ Day”, but isn’t mentioned in the 1662 Book of Common Prayer. It grew mysteriously, and is mentioned in the 2004 BCP.