Some functions in the script reference (for example, the various GetComponent functions) are listed with a variant that has a letter T or a type name in angle brackets after the function name:-
function FuncName.<T>(): T;
These are known as generic functions. The significance they have for scripting is that you get to specify the types of parameters and/or the return type when you call the function. In JavaScript, this can be used to get around the limitations of dynamic typing:-
// The type is correctly inferred since it is defined in the function call.
var obj = GetComponent.<Rigidbody>();
In C#, it can save a lot of keystrokes and casts:-
Rigidbody rb = go.GetComponent<Rigidbody>();
// ...as compared with:-
Rigidbody rb = (Rigidbody) go.GetComponent(typeof(Rigidbody));
Any function that has a generic variant listed on its script reference page will allow this special calling syntax.