I found a very good explanation about the Lambda expression in @Html.DisplayFor(modelItem => item.FirstName), see Link below.
Summary
As the author wrote, a lambda expression is a way to write an anonymous function. As a summary you can find here the lambda expression and its anonymous function it could be translated logically.
Common lambda expression
(x => x.Name)
>>>>>> translates to >>>>>>
string Function(Data x)
{
return x.Name
}
Lambda expression without left-side parameter
(() => someVariable)
>>>>>> translates to >>>>>>
string Function()
{
return someVariable;
}
Lambda expression in @Html.DisplayFor(model => item.FirstName)
model => item.FirstName
>>>>>> translates to >>>>>>
string Function(Model model)
{
return item.FirstName;
}
Here you find the complete post: I want to understand the lambda expression in @Html.DisplayFor(modelItem => item.FirstName)