I remember a time where ASP.NET WebForms was mainstream and ASP.NET MVC and Web API still had to be invented. To do a good a job as an ASP.NET WebForms developer you needed deep understanding of the ASP.NET WebForms page lifecycle. (I even got some related interview questions at the time).
These times have gone and now you should understand ASP.NET MVC and Web API both having their own lifecycle. Here is a great poster explaining the ASP.NET Web API Message Lifecycle:
And a similar one for ASP.NET MVC:
Must print material!