The Document Properties command brings up a dialog that displays information about the active Document, such as the Document title, the author, the class it was written for, etc.
The Title, Class, Teacher, and Date values are used to fill in the matching fields in the Document's Headers and Footers.
The Memo value is used to display a short note to students at the top of the first page of the Document. Advanced users can select "Treat memo text as TeX code" and use TeX commands in the memo field to do any special formatting of the memo text, such as inserting math formulas or drawing a box around the text.