"Character" - your main character, but could also be a secondary one.
"Arc" - the journey the character takes - emotional, physical, mental ... going from a starting state to a changed state at story's end
Theme - the takeaway for the reader
Look at the big giant blockbuster films that look splashy and sell well, but you walk out of there feeling not really very moved, and instead more saturated.
Let's look at a really straightforward but non-Batman example character - let's talk about Harry Potter.
He's a wizard. He's an orphan. He's relevant to a prophecy. He ages over the course of the story.
There's a lot of room for themes there, and we haven't even gotten specific with plot.
So when Harry is alone and feeling the weight of not having a lot of security in his world, you emphasize that so the reader feels it too.
Connect themes to shared emotions and arcs to emotional experiences.
Stand up to bullies -> Courage, Being Brave, Strength (
So when you're writing the scene(S) where this matters, you lean on them
Sets the relationship between characters in motion
Establishes Harry's arc progress
Confirms that peas are bad
And it's a small scene compared to others.