This command line argument indicates that the each question and each answer in the PSAE file should be interpreted as HTML, not plain text, and should be presented in a formatted way. There are several ways to do this and get a "professional" looking GUI as a result. The following screen dump shows one reasonable approach to an HTML layout for questions and answers.
Note that this approach must allow question writers to embed images in their questions and answers via the "img" html tag. You should test your system to make sure this feature works.