I do not know what a method without an access identifier is called. In this code block, I am referring to the void updateNumTo5 method.
private
The default access modifier (not identifier) is private for methods. So this:
private void Foo()
{
}
is equivalent to
void Foo()
{
}
The general rule is that the default access modifier is always the most restricted you could specify it as. So for example, non-nested types are internal by default, whereas nested types are private by default.