There are arguments to be made either way, but normally you’d scope your variables in a way that the ones specific to a particular bit of code are not accessible from elsewhere.

They're arguing to do this:

int field = 1;
void may() {
   do(field);
}

int field = 3;
void you() {
   do(field);
}

int field = 3;
void be() {
   do(field);
}

int field = 7;
void happy() {
   do(field);
}

rather than

int field = 1;
int field = 3;
int field = 3;
int field = 7;

void may() {
   do(field);
}
void you() {
   do(field);
}
void be() {
   do(field);
}
void happy() {
   do(field);
}

A bad example of encapsulation would be:

class AClass {
    private class HelloThere {
         int a = 1;
         int b = 3;
         int c = 3;
         int d = 7;
         void DoStuff(AClass self) {
              Do(a, b);
         }
    }
    private HelloThere field = new();
    void World() {
        field.DoStuff(this);
    }
}

Of course, there is nuance here. Is this class encapsulating enough that it's got a right to exist? That'll depend on the situation.

Also, c has local static variables. Depending on your use case, it might just be easier in c than in C# and similar.

// a method with a state, horrid in some contexts, great in others
void PrintCounter() {
    static int count = 0;
    Print(count);
    count += 1;
}

And just in case you're still reading and curious:

#region PingPong
    // hi! I am in a region, collapse me using your ide!
#endregion