What is the purpose of Java DOT operator?

Can somebody tell me what Java DOT operator actually does?

For example:

public class {
    int value;
    public void great() {};
    ... 
}

public static void main(String[] args) {

    Person p = new Person();

    Person.great(); // <--- here

    Person.value; // <--- here

I want to know what is . operator doing in above code when I do Person.great() or Person.value?