Complex sentence: Whereas a child fire-setter is usually curious about fire and has the desire to learn more about fire, a child pyromaniac is more than just a simple fire-setter; he is one who has an unusually bizarre impulse or desire to set intentional fires.
Split into simpler sentences: Whereas a child fire setter usually is curious about fire and has the desire to learn more about fire. A child pyromaniac is more than just a simple fire setter; he is one who has an unusually bizarre impulse or desire to set intentional fires.