Learn Core Java : call a constructor from same class constructor using this() constructor chaining

what is this() construct? How to call ( invoke ) a constructor from another constructor of the same class. Constructor chaining. error: call to this must be first statement in the constructor. error: recursive constructor invocation. calling no argument constructor from parameterized constructor. calling parameterized constructor from no argument constructor. calling parameterized constructor from another parameterized constructor. what is the difference between this keyword and this() construct?