Jerusalem is important to Judaism, Christianity, and Islam because it's home to many holy sites and is considered the birthplace of Judaism.
Importance to Judaism
The birthplace of Judaism, where creation began
The site of many key events, including the establishment of Jerusalem as the capital by King David
Importance to Christianity
The site of many key events in Jesus' final week, including his death, crucifixion, and resurrection
The site of the Church of the Holy Sepulchre
Importance to Islam
The site of the Dome of the Rock, where Muslims believe Muhammad ascended to heaven
The site of the al-Aqsa mosque, which Muslims faced in prayer before the direction was changed to the mosque in Makka
Other significance
Jerusalem is one of the oldest cities in the world
It's been conquered, destroyed, and rebuilt many times
It's the most fought over piece of land in history