The Sicilian Defence is by far Black's most popular answer to 1 e4 at all levels of chess. The reason is easy to understand: from the very first move Black unbalances the position and can play for a win without needing to take unjustified risks. This is particularly the case with the Open Sicilians, where Black can take comfort in the fact that his superior pawn structure ensures control of the centre and excellent long term chances.
Faced this with type of problem, along with the fact that many Open Sicilians carry with them a massive build-up of opening theory, it's unsurprising that many White players prefer to avoid the Open Sicilian altogether, preferring one of the many 'Anti-Sicilians' lines on offer.
