Maybe it is not too late to add some info.
Sum:
The Func is a custom delegate defined in System namespace that allows you to point to a method with the same signature (as delegates do), using 0 to 16 input parameters and that must return something.
Nomenclature & how2use:
Func<input_1, input_2, ..., input1_6, output> funcDelegate = someMethod;
Definition:
public delegate TResult Func<in T, out TResult>(T arg);
Where it is used:
It is used in lambda expressions and anonymous methods.