Bayes Filtering is a way of separating 'junk' or unwanted emails from the emails that you want to receive. It does this by looking at what words are in the email, who it is from and who it is addressed to and then deciding if it is something you would want to read. It remembers what emails you have opened and which ones you have not. The more emails you read, the better it gets at picking out the ones you would like to read.