  In this article, we will research the Recommender System's implementation
about how it works and the algorithms used. We will explain the Recommender
System's algorithms based on mathematical principles, and find feasible methods
for improvements. The algorithms based on probability have its significance in
Recommender System, we will describe how they help to increase the accuracy and
speed of the algorithms. Both the weakness and the strength of two different
mathematical distance used to describe the similarity will be detailed
illustrated in this article.
