In the Sicilian we get pretty much the same themes that we already know from 1… e5. Most lines in the Sicilian are based on attacking the e4-pawn with Nf6, therefore the Sicilian is typically more aggressive than the attempts to trade off the e4-pawn.
A. Alekhine-Theme (Nimzowich)
B. Pirc-Theme (Dragon)
C. Petroff-Theme (Sveshnikov)
White on the other hand can also try to follow typical patterns known from 1… e5:
A. Ponziani-Theme (Alapin)
B. Vienna-Theme (Closed)
C. Ruy Lopez-Theme (Rossolimo)
C. Scotch-Theme (Open Sicilian)
… and that’s it.
The Sicilian is very similar to 1…e5, except there is a pawn on c5. From that point on it’s just forced lines like in most variations after 1.e4. The only Sicilians where black doesn’t attack the e-pawn at an early stage are the Paulsen/Taimanov systems. The resulting development of pieces is closely related to the French, except the black d-pawn is more flexible. Even transpositions are possible.