Java static

static

 members
belong to the class instead of a specific instance.

It means that only one instance of a 

static

 field
exists[1] even if you create a million instances of the class or you don't create any. It will be shared by all instances.

Since 

static

 methods
also do not belong to a specific instance, they can't refer to instance members (how would you know which instance Hello class you want to refer to?). 

static

 members
can only refer to 

static

 members.
Instance members can, of course access 

static

 members.

Side note: Of course, 

static

 members
can access instance members through an object reference.

Example:

public class Example {
private static boolean staticField;
private boolean instanceField;
public static void main(String[] args) {
// a static method can access static fields
staticField = true;

// a static method can access instance fields through an object reference
Exam
4000
ple instance = new Example();
instance.instanceField = true;
}

[1]: Depending on the runtime characteristics, it can be one per ClassLoader or AppDomain or thread, but that is beside the point.