>>2 This, though the example given was kind of obvious.
Another example, which is the one I got when I learned this.
The Giving Tree- You never know what you have until it's gone.
Theme is often confused with the actual plot of the story because the plot and the theme often go hand in hand, but I've never come across an example where it's the exact same thing.
If you're really stuck on this, ask, "What can I learn from this" or "What kind of underlying morals are in this story." IF you want to practice it, read Dr. Seuss and try to find the themes in his books. He's someone who actually puts it in there, which is why adults like his books too.
I think the theme of my book might end of being something on the lines of, "All our dreams can come true, if we have the courage to pursue them." -Walt Disney. I'm not sure since I haven't finished writing it, but I did not intentionally put that theme in there on purpose.