I am watching videos about the London system, and one example they use is this game.
[Title "Carlsen-Ghaem, Baku 2016"] [FEN ""] 1. d4 d5 2. Nf3 Nf6 3. Bf4 e6 4. e3 Bd6 5. Bg3 c5 6. c3 Nc6 7. Nbd2 Bxg3 8. hxg3 Qd6 9. Bb5 Bd7
after 8. ... Qd6, the guy explaining the video says that Black is preparing to move e5, so White moves 9. Bb5 to avoid that. What is Black's plan with that move?