// This declaration announces the existence of a variable named firstName, of type TextView.

TextView firstName;

// Now that we have declared the variable textView, we can go ahead and use it.

// For example, we can assign a value to it (store a value into it).

firstName = (TextView)findViewById(R.id.firstName);

// But the following statement will give us an error message because we have never declared any variable named lastName.

lastName = (TextView)findViewById(R.id.lastName);