Exchange Variation
Caro-Kann Defense
1.e4 c6 2.d4 d5 3.exd5 cxd5
White trades on d5, leading to a symmetrical pawn structure.
Fun fact: In 1970, Bobby Fischer beat Tigran Petrosian in this line with the new move 11.a4!, and most Black players have avoided that line since. Source
Practice this lineThe idea
White exchanges on d5, and Black recaptures with the c-pawn. The pawns are now symmetrical, and both sides have an open c-file and a half-open e-file.
The main line is 4.Bd3, which stops Black from developing the bishop to f5. A usual continuation is 4...Nc6 5.c3 Nf6 6.Bf4 Bg4 7.Qb3, where White's queen hits b7 and d5. White's other big option is 4.c4, the Panov-Botvinnik Attack.
Plans for White
With 4.Bd3 and c3, White builds a solid setup, places the bishop on f4, and uses Qb3 to put pressure on Black's queenside. A knight on e5 is one of White's typical goals.
The edge is small but lasting, and Black has to play accurately to equalize.
Plans for Black
Develop with ...Nc6, ...Nf6 and ...Bg4, and meet the pressure on b7 with ...Qd7 or ...Qc8. The structure resembles the Carlsbad structure from the Queen's Gambit with colors reversed, so Black can consider a minority attack with ...b5 and ...b4 later.
Watch out for
For Black, the old 7...Na5 against 7.Qb3. It looks active, but after 8.Qa4+ Bd7 9.Qc2 Qb6 10.Nf3 e6 11.a4!, as Fischer played against Petrosian, White's bishop on d3 is better than Black's on d7 and White has a slight, stable edge. Most players now prefer 7...Qd7 or 7...Qc8.
For White, the danger is playing too quietly. The symmetrical structure is drawish, so a White player who just develops without a plan gives Black an easy game.