Classical Variation, Advance Variation

Rather than release the central tension with 9...cxd4, Black advances 9...c4. This avoids the isolated d-pawn and gains queenside space, but it gives up pressure on d4 and leaves the c4-pawn as a target. White most often answers 10. Ne5, placing the knight on the e5 outpost. 10. b3 instead strikes at the advanced pawn directly, while 10. e3 is a quieter way to reinforce d4. The engine rates the position as roughly balanced, and practical results are fairly close.