A universal theme is often (A) a central message that applies to anyone, anywhere.
For example, in the To Kill a Mockingbird, the central theme is the 'death' of innocence. This is a universal theme in a way that in everyone's lives at some point, there comes a time where their innocence is shattered....whether they are growing up or have witnessed something that they shouldn't have. As such, this is applicable to anyone, anywhere.