The Beta Family

The Beta distribution is a family of continuous distributions on [0,1] with two parameters (commonly known as $\alpha$ and $\beta$, but also $r$ and $s$).

Beta distributions are commonly used in situations where we want to continually update a prior distribution given new information.

• The beta (1,1) distribution is identical to the uniform distribution.

http://prob140.org/textbook/content/Chapter_21/00_The_Beta_and_the_Binomial.html