I assume you are talking about return types, as in: private void myMethod () void means the method does not return anything. boolean is a variable type that can be used to hold the value "true" or "false" (it can be thought of as similar to a light switch - either on or off). These are the basics of methods, which is grade 11 curriculum in my region. You should probably find a tutorial on Java if you want a full understanding.

Since nobody actually mention anything about 'void', I will say this: 'void' is the absence of a data type; similar to how 'null' is the absence of an object. I do not know of any other use for 'void' other than as a return type in a method declaration statement.