What is the difference between application variable and session variable?

Application variables are the variables which remain common for the whole application… Their value can be used across the whole application… And they die only when the application stops or probably when they are killed forcibily… The ideal example for these kindof variables are site counter… We can find out how many people accessed a particular site since the time it went live via application variables and incrementing the same on ever session start..
Session variables are variables which remain common for the whole application but for one particular user. They also can be used across the whole application… But they die when a particular user session ends or probably when they are killed forcibily… The ideal example for this kindof variable are user id… You might want to show "Welcome Vishal" on every page of your site till vishal logs off… So in session start you set a variable to "Welcome Vishal" and kill it on session end…
All these methods like session start, session end, application start, application end are found in global.asax and that’s the reason global.asax is one for the whole ASP.Net application…
I hope this provides you with the info that you needed…