What is the big idea

"What's the big idea?"
Seems like a simple question, doesn't it?
I ask myself this question about art in general, and about my art in particular. When I look at a photograph or a painting, or any other piece of art, for that matter, I want to understand the "big idea" behind the art. Is it about color and shapes? About textures? Does it make me rethink my view of a person or a place or an idea?
When I am painting, I often start with color(s) and general shapes and wait until I see some "big idea" starting to form.
What about you? When do you ask "What's the big idea?"