That's a lambda expression. When an expression works on a type it is written in the format of
(x => ...)
"x" is arbitrary, it can be anything you want, it is effectively a temporary variable of the type that the expression works on. So for;
List<string> myData = new List<string>();
myData.Where (abc => abc != "Hello);
What we're saying in the "Where" left of the "=>" is that abc is a variable of type string, and right of the => is the expression we want to evaluation, so where the data in abc is not Hello. The Where will then loop through each instance in the list, load that instance into the variable abc, and then check if abc != "Hello".
So there is no significance to what you call the variable, it could be "model", "m" or even
@Html.DisplayNameFor(supercalifragilisticexpialidocious => supercalifragilisticexpialidocious.SomeObjectName)
People tend to chose model or m as it makes it obvious what the function is acting on. Just don't confuse that "model" with the "@model" directive at the top of the view, or the "Model" property :)