Technically, a ball is 'on' if it can be legally struck by the cue ball. However, the term is most often used to mean that a ball can be potted. For example, if the term was used in commentary e.g 'There are no reds on', this is unlikely to mean the player is snookered (as it technically should), rather that no reds are in potable positions.
There is only one white ball - the cue ball. It is the only ball which is not meant to be potted at any time.
The white ball in Snooker is called the "Cue Ball".
Makes no sense grammatically. The white ball is the cue ball in snooker.
Potting the brown ball in snooker earns you 4 points.
The pink ball
cue ball
A snooker in pool can be deliberate (by your opponent) or accidental (by yourself). It is when the a straight line path from the cue ball to the object ball is blocked by another ball which may not be hit.
It basically means is it possible? If a ball is pottable, the ball is on.
The green ball is worth three points in snooker.
Pink
No
Yes, but it is not played anymore.