Very big. Billiards and the pocket billiards games have many millions of players worldwide and in many countries. In the US alone, there are over 32 million pool and billiards players. With tournaments, leagues, pool halls and the equipment it is a many billion dollar industry.
By watching the most skilled players and practising.
In English Billiards, a cannon is a shot that hits both the red ball and the players cue ball in the same shot. This shot scores 2 points. The cannon does not exist in pocket billiards.
There is no synonym for billiards.
Professional billiards players generally do not get a salary. However, they can earn up to $30,000 a year even as beginning professinals.
In English Billiards, a cannon is a shot that results in hitting both the red ball and the players cue ball and results in 2 points.