Simplify the following text for a Grade 6 native English-speaking person.
Original: Good Friday ( from the now obsolete senses pious , holy of the word `` good '' ) , also known as Holy Friday , Great Friday , is a religious holiday observed primarily by Christians commemorating the crucifixion of Jesus Christ and his death at Calvary .
Simplified: Good Friday is a religious holiday usually observed by Christians . It is also called Holy Friday , Black Friday , or Great Friday .