This opening was used a lot by the great Bent Larsen. He called it the baby orangutan. He used this opening and won many great games.
After b3, black will usually play e5 or d5. White lets black grab the center but hits it with Bb2, Nf3, and c4. White wants to show that black's center is weak, black will try to make it undestructable. that's what this opening is about. Feel free to comment and enjoy!