The information on their introductory page explains their mission and vocation as follows:
The strength of the Church, and the state of our world, rests in the people of God living their Faith to the full. Those who live committed to Christ transform the world through the Savior's actions in and through them. This means treating God as a "loved one." As we spend time with those we love, they change and add meaning to our lives. If we do not live a committed Christian life now for the love of God, we will probably never live it.
The Rule of 1221 is the foundation Rule of the Brothers and Sisters of Penance. Both ancient and holy, its tenets were the basis of many medieval penitential groups and Third Orders and the life-path of many Saints and Blessed within the Church. It stands forever as a call to lay people to follow fearlessly the path of the Lord and His Saints. Its lifestyle is timeless and holy, completely authentic in its call to personal conversion.
I'd recommend that anyone who is interested in the Camino de Santiago, whether or not you've done it yet, check out the information on their web page. For those who have made a pilgrimage along the Camino and who have felt the call to keep alive the experience of simplifying your existence in order to facilitate the Interior Camino towards God, this site will provide you with a lot of excellent information as to how to do that. I have found reading through the information about the Rule of 1221 enormously helpful, and I've begun adopting some of its practices. A wonderful site.