Simplify the following text for a Grade 14 native English-speaking person.
Original: The core of the PropÃ dia is its Outline of Knowledge , which seeks to provide a logical framework for all human knowledge ; however , the PropÃ dia also has several appendices listing the staff members , advisors and contributors to all three parts of the Britannica .
Simplified: The core of the PropÃ dia is its Outline of Knowledge , which is supposed to give people a classification of what we know , but the PropÃ dia also has some parts listing the staff members , advisors and contributors to all three parts of the Britannica .