Earth-295, also known as the Age of Apocalypse, is an alternate Marvel timeline in which Charles Xavier was killed at a young age and Erik Lehnsherr formed the X-Men and carried out Xavier's dream of a world where humans and mutants could live together in peace. The Earth-295 reality began at the point of Xavier's death.
The future son of Xavier in the Prime Universe (Earth-616) timeline, a timeline in which Erik was a villain, traveled back in time to kill Erik before he could become evil. During the fight, Xavier sacrificed himself to save his friend Erik. Xavier's death would cause a paradox. As the Earth-616 timeline began to fall apart, the M'Kraan Crystal warped time and space to create a new reality, Earth-295.