Simplify the following text for a Grade 5 native English-speaking person.
Original: It is a legislative institution with the authority to supplement and apply the laws of BahÃ ` u 'll Ã h , the founder of the BahÃ ' Ã Faith , and exercises a judicial function as the highest appellate institution in the BahÃ ' Ã administration . The institution was defined in the writings of BahÃ ` u 'll Ã h and ` Abdu ` l-Bah Ã , BahÃ ` u 'll Ã h 's successor , and was officially established in 1963 as the culmination of the Ten Year Crusade , an international BahÃ ' Ã teaching plan .
Simplified: It was described by the person who made the BahÃ ' Ã Faith , BahÃ ` u 'll Ã h , in his books and letters .