Sicilian Defense: Old Sicilian - Magnus Carlsen Best 15

Sicilian Defense - A Total Guide (with White's Response)

File:Old Sicilian, Open, Accelerated Dragon Variation of the

Is the Sicilian french variation the best variation in the

Sicilian Defense: The Chelyabinsk Variation

Sicilian Defense: Old Sicilian Variation - Chess Openings

Sicilian Defense: Moscow Variation

The Modernized Anti-Sicilians – Volume 1 – Rossolimo Variation - Thinkers Publishing

Why would White play 2.a3 as their 2nd move in the Sicilian Defense? It's not an accepted opening and I see no benefits. How would you go about strategizing a reply, as

The Sicilian with . . . Qb6 / Dynamic surprise weapons, AND A SECOND BOOK, play 1e4 e5! / a complete repertoire for Black in the Open Games, AND A THIRD BOOK

I'm trying to understand the Sicilian Defense - Kramnik Variation (1.e4 c5 2.Nf3 e6 3.c4). Can someone, in simple terms, explain to me why Black's response of a forceful d5 is such