class Student
public String name = "John Doe";
public int type = 0;
public int tutor = 2;

public Student(String n, int s, int t)
{
this.name = n;
this.type = s;
this.tutor = t;
}

}

This refers to the current class.

It is more useful when inheriting as you can call an inherited method
using this, which would have been quite hard to do if this did not
exist.

What I have done in the above example  is to set attributes to
parameters.

i'd like to say that there is a case you must
use "this" keyword this case if the parameter or a function  the same
as the attributes of the class like this example

class Student
{
private String name;
private int age;
private String email;
public Student()
{
name="";
age=0;
email="";
}
public Student(String name,int age,String email)
{
this.name=name;
this.age=age;
this.email=email;
}
}