What's the use of HttpContext.Current?

I'm reading a book and trying out the exercises.
One @helper code uses HttpContext.Current.Request[option] 
while mucking around with the code, an equivalent (and simpler) 
string varState = Request.Form[option]; 
could accomplish the same thing. 
So my question is why is HttpContext.Current needed?  What benefit does it give you? 
According to MSDN, the class HttpContext "Encapsulates all HTTP-specific information about an individual HTTP request." 
But if the  varState = Request.Form[option] can also access the same form value, why bother with adding HttpContext.Current?    
What cases is this needed or required?  Looking for insights.