1.e4 c6
In the Caro Kann Defense, black does not immediately challenge the white center. White should therefore immediately place another pawn there with 2.d4. Black will counter with 2...d5.
The advantage of this defense is that, unlike the French Defense, the black pawn structure does not imprison the black's white squared bishop on c8. In many lines of the Caro-Kann, black will develop this bishop to f5 or g4 before playing e6. On the other hand, the pawn on c6 robs the black knight on b8 of its natural developing square.
By the third move, white has an important decision with the pawn on e4. This pawn is under attack. White can therefore choose among three options: to capture on d5, to push the e-pawn to e5, or to defend the pawn with Nc3 or Nd2. The e5 push has become popular in recent years among masters, but all three choices remain viable.
Sources for further reading
R.Keene et al, UNDERSTANDING THE CARO KANN DEFENSE, RHM Press, 1980
A.Karpov and A.Beliavsky, CARO-KANN IN BLACK AND WHITE, R&D Publishing, 1994
E.Varnusz, PLAY THE CARO-KANN, Maxwell MacMillan, 1991