The Great Escape was a real event during World War 2. It was a huge undertaking by the Allied POWs. They used their skills and ingenuity to try to break free. The Germans had a very secure camp, but the prisoners were determined. In the end, though many were recaptured, it showed the indomitable spirit of the Allied forces and became a famous story of resistance in the face of the enemy.
One key element was the tunneling. The prisoners dug tunnels to get out of the camp. Another was the teamwork. Different prisoners had different skills and they all worked together. Also, the diversion tactics were important, like creating distractions to keep the guards' attention away from the escape preparations.
The Great Escape had its roots in true history. But keep in mind that when turned into a film or story, details might be changed or enhanced to hold the audience's interest.
In a way, it is. The movie takes elements from actual escape attempts and consolidates them into a fictional narrative. However, there are creative liberties taken for entertainment purposes.