Application and Cache

Hi
I have a few questions on the asp.net application and the cache.
1. where is the cache?
2. is the cache cleared when the application restarts?
3. when is an asp .net application ended or restarted?
3a. how long is an application variable available?
 
im a litte unclear on the lifespan of an asp .net application and therefor that of the cache.
 
thanks in advance
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