Simplify the following text for a Grade 5 native English-speaking person.
Original: Peter Waldo , Valdo , or Waldes ( c. 1140 -- c. 1218 ) , also Pierre VaudÃ s or de Vaux , is credited as the founder of the Waldensians , a Christian spiritual movement of the Middle Ages , descendants of which still exist in various regions of southern Europe .
Simplified: Peter Waldo , Valdo , or Waldes ( c. 1140 -- c. 1218 ) , also Pierre VaudÃ s or de Vaux , is believed by many to have started the Waldensians . This was a Christian spiritual movement of the Middle Ages .