Bayes theorem is a mathematical formula used to determine conditional probabilities of events. It was discovered by English statistician Thomas Bayes in 1763. The formula is P(A/B)= P(B/A)P(A)/P(B), where P(A/B) is the probability of event A occurring given that event B has occurred, P(B/A) is the probability of event B occurring given event A, P(A) is the probability of event A, and P(B) is the probability of event B. The document provides an outline of Bayes theorem and the total probability theorem.