What is the difference between an Apostolic Exhortation and an Encyclical Letter? Pope Francis has just released an Apostolic Exhortation called Evangelii Gaudium (The Joy of the Gospel). He also released an Encyclical Letter in the summer called Lumen Fidei (The Light of Faith). What is the difference between these two types of documents? Is one considered to be more important than the other?
Apostolic Exhortation is a type of communication from the Pope that is written to encourage people to undertake an implementation of particular set of recommendations listed in the document.

Encyclical Letter which is usually more important than Apostolic Exhortation is a letter that usually deals with a specific doctrine, where the doctrine is clarified, or explained in greater detail.