On the Challenge website, Lady Albreda writes:
Challenges have long been a part of Scadian culture, and I thought that a challenge of 50 things seemed appropriate for our 50th year. Since years in the SCA are counted as Anno Societatis (year of the Society), or AS, and Arts and Sciences (the lovely canopy under which so many of my interests rest) is oft abbreviated A&S, the A&S 50 Challenge was born.
The A&S 50 Challenge can take one of two forms; either Depth or Breadth. The Depth Challenge is to create/do 50 of any one thing - make 50 pairs of shoes for your Shire, pen 50 scrolls for your Kingdom signet, cast 50 coins blanks, make 50 pieces of garb, judge 50 competition entries, teach 50 classes, perform 50 songs, or even write a 50 page research paper; if you want to take your current work to a new level, doing 50 of it is bound to carry you a long way towards that goal! The Breadth Challenge can be about either trying new things, (either completely new to you, variations on things you have done before, or even new to your household, local group, or even Kingdom), or about creating a complete persona package (things that your persona would know about, have, and know how to do). Both individuals and groups may enter, and can choose to complete as many Challenges of either type as they please!
The purpose of the Challenge is twofold; to learn and share of our learning, and to create and share of our creation. While we are edifying and beautifying our fair lands, we will also be serving both our populace and The Dream, and helping to make the SCA the very best it can be as it enters its 50th year.