Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Ba4/4...Nf6/5. O-O/5...Be7/6. Re1/6...b5/7. Bb3/7...d6/8. c3/8...O-O/9. h3/9...Na5

Chigorin Defense
This is the old main line. Black chases white's bishop from the effective a2-g8 diagonal. Not only that, black opens up the c-pawn to expand on the queen side. Usually, after 10. Bc2 and 10…c5, if allowed, black will play 11…Nc6 and black ends up with a space advantage on the queen side.