each time i start mine craft go on a world it crashes

Put the summary of the bug you're having here
i start up a world it crashes
What I expected to happen was...:
Describe what you thought should happen here
the world would open
What actually happened was...:
Describe what happened here
i was playing minecraft and it crashed and it keeps crashing
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...