Simplify the following text for a Grade 7 native English-speaking person.
Original: Pope Leo XIII ( 2 March 1810 - 20 July 1903 ) , born Vincenzo Gioacchino Raffaele Luigi Pecci to an Italian comital family , was the 256th Pope of the Roman Catholic Church , reigning from 1878 to 1903 .
Simplified: Pope Leo XIII ( March 2 , 1810 â '' July 20 , 1903 ) , born Vincenzo Gioacchino Raffaele Luigi Pecci , was the 256th Pope of the Roman Catholic Church . He held the office from 1878 to 1903 .