The object of the game is to score more points than the opponent by potting object balls in a predefined order. At the start of a frame, the balls are positioned as shown and the players take it in turns to hit a shot in a single strike from the tip of the cue, their aim being to pot one of the red balls and score a point. If they do pot at least one red, then it remains in the pocket and they are allowed another shot - this time the aim being to pot one of the colours. If successful, then they gain the value of the colour potted. It is returned to its correct position on the table and they must try to pot another red again. This process continues until they fail to pot the desired ball, at which point their opponent comes back to the table to play the next shot. The game continues in this manner until all the reds are potted and only the 6 colours are left on the table; at that point the aim is then to pot the colours in the order yellow, green, brown, blue, pink, black. When a colour is potted in this phase of a frame, it remains off the table. When the final ball is potted, the player with the most points wins.
Points may also be scored in a game when a player's opponent fouls. A foul can occur for numerous reasons, such as hitting a colour first when the player was attempting to hit a red, potting the cue ball, or failing to escape from "a snooker" (a situation where the previous player finished their turn leaving the cue ball in a position where the object ball cannot be hit directly). Points gained from a foul vary from a minimum of 4 to a maximum of 7 if the black ball is involved.
One game, from the balls in their starting position until the last ball is potted, is called a frame. A match generally consists of a predefined number of frames and the player who wins the most frames wins the match overall. Most professional matches require a player to win five frames, and are called 'Best of Nine' as that is the maximum possible number of frames. Tournament finals are usually best of 17 or best of 19, while the World Championship uses longer matches - ranging from best of 19 in the qualifiers and the first round proper, up to 35 frames in length (first to 18), and is played over two days.
Professional and competitive amateur matches are officiated by a referee who is the sole judge of fair play. The referee also respots the colours on to the table and calls out how many points the player has scored during a break. Professional players usually play the game in a sporting manner, declaring fouls the referee has missed, acknowledging good shots from their opponent, or holding up a hand to apologise for fortunate shots.
Other terminology used in snooker includes a player's break, which refers to the total number of consecutive points a player has amassed (excluding fouls) when at one visit to the table. A player attaining a break of 15, for example, could have reached it by potting a red then a black, then a red then a pink, before failing to pot the next red. The traditional maximum break in snooker is to pot all reds with blacks then all colours, which would yield 147 points; this is often known as a "147" or a "maximum". See also: Highest snooker breaks.
Accessories used for snooker include chalk for the tip of the cue, rests of various sorts (needed often, due to the length of a full-size table), a triangle to rack the reds, and a scoreboard. One drawback of snooker on a full-size table is the size of the room (22' x 16' or approximately 5 m x 7 m), which is the minimum required for comfortable cueing room on all sides. This limits the number of locations in which the game can easily be played. While pool tables are common to many pubs, snooker tends to be played either in private surroundings or in public snooker halls. The game can also be played on smaller tables using fewer red balls. The variants in table size are: 10' x 5', 9' x 4.5', 8' x 4', 6' x 3' (the smallest for realistic play) and 4' x 2'. Smaller tables can come in a variety of styles, such as fold away or dining-table convertible.
Governance and tournaments
|World Series of Snooker|
|See: Snooker tournaments|
The World Professional Billiards and Snooker Association (WPBSA, also known as World Snooker), founded in 1968 as the Professional Billiard Players' Association, is the governing body for the professional game. Its subsidiary, World Snooker, based in Bristol, England, organises the professional tour. Over the years the board of the WPBSA has changed many times, which some argue is an indication of in-fighting within the sport. The amateur game is governed by the International Billiards and Snooker Federation (IBSF).
Professional snooker players can play on the World Snooker main tour ranking circuit. Ranking points, earned by players through their performances over the previous two seasons, determine the current world ranking. A player's ranking determines what level of qualification they require for ranking tournaments. The elite of professional snooker is generally regarded as the "Top 16" ranking players, who are not required to pre-qualify for any of the tournaments. The tour contains 96 players - the top 64 from the previous two seasons, the 8 highest one-year point scorers who are not in the top 64, the top 8 from the previous season's Pontin's International Open Series (PIOS), and various regional, junior and amateur champions.
The most important event in professional snooker is the World Championship, held annually since 1927 (except during the Second World War and between 1958 and 1963). The tournament has been held at the Crucible Theatre in Sheffield (England) since 1977, and was sponsored by Embassy from 1976 to 2005. Since 2005, tobacco companies have not been allowed to sponsor sporting events in the United Kingdom, and the World Snooker Championship had to find a new sponsor. It was announced in January 2006 that the 2006–2010 world championships would be sponsored by online casino 888.com. The Championship is currently sponsored by BetFred.com after 888.com pulled out of their five year sponsorship deal after three years. On 15th April 2009 the World Snooker Championship website announced that Betfred.com would be the new sponsor of the World Championship for the next four years.  
The status of winning the World Championship is great, and it is the most highly valued prize in professional snooker, both in terms of financial reward (£250,000 for the winner) as well as prestige. The World Championship is televised extensively in the UK by the BBC and gains significant coverage in Europe on Eurosport and in the Far East.
The group of tournaments that come next in importance are the other ranking tournaments. Players in these tournaments score world ranking points. A high ranking ensures qualification for next year's tournaments, invitations to invitational tournaments and an advantageous draw in tournaments. The most prestigious of these after the World Championship is the UK Championship. Third in line are the invitational tournaments, to which most of the highest ranked players are invited. The most important tournament in this category is The Masters, which to most players is the second or third most sought-after prize.
In an attempt to answer criticisms that televised matches can be slow or get bogged down in lengthy safety exchanges and that long matches causes problems for advertisers, an alternative series of timed tournaments has been organised by Matchroom Sport Chairman Barry Hearn. The shot-timed Premier League Snooker was established, with seven players invited to compete at regular United Kingdom venues, televised on Sky Sports. Players have twenty-five seconds to take each shot, with five time-outs per player per match. While some success has been achieved with this format it generally does not receive the same amount of press attention or status as the regular ranking tournaments.
There are also other tournaments that have less importance, earn no world ranking points and are not televised. These can change on a year-to-year basis depending on calendars and sponsors.