The Smith Morra gambit is a variation of the Sicilian defence in which White sacrifices a pawn right in the opening to get a small long term positional advantage.
It is questionable if this slight edge justifies to sacrifice an important center pawn, the c-pawn.
This opening is very seldom played at grandmaster level. After all White has already a small edge as he has the first move, why should he sacrifice a valuable center pawn?
Nonetheless Amateur players believe that this is the true way to avoid the dangerous waters of the Sicilian defence, which is the best defence for Black as it has the best records.The moves are:
If Black captures the pawn 3...dxc then White recaptures with the knight and develops a piece. After that he sets himself up as follows: Nf3, Bc4, 0-0, Qe2, Rfd1 pushes the e-pawn to e5 and controls both the c and d files with his rooks.
White gets pressure along the d-file and is slightly better developed. This setup leads to a small long-term positional compensation for White, but he has to keep the flame burning or his slight edge will simply disappear and he is a pawn down.
If Black can't stand the psychological pressure and makes slight errors he can easily get a bad position and lose. It is doubtful if the sacrifice of a center pawn (c-pawn) is justified just to gain one tempi. This is probably the reason why it is never played at top level chess.
A typical position, the Classical Mainline arises after 3...d4xc3 4. Nb1xc3 Nb8-c6 5. Ng1-f3 e7-e6 6. Bf1-c4 d7-d6 7. 0-0 Ng8-f6 8. Qd1-e2 Bf8-e7 9. Rf1-d1 e6-e5 10.h3 with long term compensation for the pawn. (see diagram above)
Siberian Variation: After 5... e7-e6 6. Bf1-c4 Ng8-f6 7. 0-0 Qd8-c7 8. Qd1-e2?! Nf6-g4! 9. h2-h3 ?? (or 9. Bc4-b3 ??) Nc6-d4! White falls for the "sibirian trap". (see diagram above)
Black can avoid the Smith Morra gambit by playing 3...d5, if White captures 4.exd Qxd, the black queen can't be attacked by Nc3 as the c3-square is blocked temporarily by the c-pawn. This can lead to the following comfortable position for Black. (see diagramm above)
Black is scoring very well with the Morra Gambit. Don't waste your time with this opening if you take chess serious and want to become a good player. If you play it, you simply give away the slight natural advantage that you have, playing the white pieces, because you sacrifice an important center pawn. That's all there is to it.