411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. Nc3/3...dxe4/4. Nxe4/4...Bf5/5. Ng5/5...Bg6/6. N1f3/6...h6/7. Ne6/7...fxe6/8. Ne5
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Knight lands on e5, controlling black king's escape squares. Because of doubled pawns, black side has turned into bipolar world - Queenside and Kingside, when the last one has been ruined. Best response as black would be Be4, but the most popular is Bf7?, which at the first sight helps to defend the king, but later causes only more problems. The main counterattack for white is usually either Bc4, but sometimes you can attack right after that with Qh5+.