Before going into Partially applied Functions, let me introduces 2 terms-
Function Literal- This exists in the source code- Something similar to Class definition. So we have
(x:Int,y:Int) => x+y
Function value- When this function literal is assigned to a reference they become function values. The are similar to the Objects created from the class. These are created at runtime
var sum = (x:Int,y:Int) => x+y
So in the above case we can use sum to invoke the method.