Java8 lambda expression-syntax

What is the lambda expression, in the encyclopedia explanation is

A lambda expression is an anonymous function, which is named after the lambda calculus in mathematics and directly corresponds to the Abstraction), is an anonymous function, that is, a function without a function name. A lambda expression can represent closures (notice differs from the traditional mathematical sense).

In Java I understand that it is an anonymous class, or an argument expression ( an executable block of code with parameters ).

(Type1 param1, Type2 param2, ..., Typen paramn), {  statment1;  Statment2;  //.............  return STATMENTM;}

Multi-parameter Lambada expression (java8 pseudo-code):

JAVA8: (int x,int y)->{ return x+y; }; or (int x,int y) (x+y), or (x, y)-> (x+y);

JAVA8 before: int add (int x,int y) {

return x+y;

}

Single-parameter Lambada expression

j ava8:  (int x)- >{  return x ;     (x), or   x-> (x);

Non-parametric Lambada expression

JAVA8: ()---(.....)

Java8 lambda expression-syntax