title: Application_Start Vs Session_Start
body: <p>Actually I am new to ASP.NET and I came through these concepts. 
  What is the difference between <code>Application_Start</code> Vs <code>Session_Start</code>?</p>
  
  <p>And also how to know how many users are currently active in our application? Is by using <code>Application_Start</code> or by using <code>Session_Start</code>?</p>