The main move now is 5...h6, kicking the Bishop. This is the Moscow Variation. The Bishop usually retreats to h4. The Bishop gets another prod by 6...g5 and after 7.Bg3, Black can take on c4 and shore up his prize with 8...b5.
So does White have enough compensation for his c-pawn? In recent years top players have become far more optimistic about White's position in this once scorned line. They have found that White's impressive center gives him good chances against Black's somewhat loose Kingside after 8.Be2.
This former sideline is now a well beaten path at the top table of world chess. It is heavily analyzed and rich in theory with many, many GM games. Several variations have sprung from this position and it pays to go to school before trying it in the field.