Like every competitive sport, table tennis has its own set of rules and regulations which aim to regulate what is acceptable for facilities (court size, ceiling height, floor covering, lighting), equipment size and materials, playing rules, clothing, etc..  The objective of the regulations is to ensure that playing conditions and playing practices are fair to everyone and in the sport's best interest.

The rules and regulations change periodically to address evolutions in the sport.  A few examples:

• in response to an ever increasing ability to spin the ball resulting from advancements in inverted rubbers introduced in the early 1950s (rubbers with smooth surfaces and pimples facing inward which allow the rubber to grip the ball and for the ball to spring off the racket), "anti-spin" rubbers (rubbers which were quite "dead" and "slippery") were introduced in the late 1970s.  It wasn't long before some players figured out that if they put a very grippy rubber on one side of their racket, and an anti-spin rubber on the other side, that the variation in spin and speed caused their opponents to misjudge the spin and the bounce of the ball, and to miss their return shots entirely (hitting the ball into the net or over the table).  The ability to confuse the opponent became even more pronounced if a player periodically twirled their racket in their hand to mix which of the two rubbers was being used to hit the ball.  One very common tactic was to twirl the blade under the table, out of sight of the opponent, and then quickly serve the ball, leaving the opponent very little time to decide during the return which of the two rubbers was used for the service.  Because at that time, the rubbers could be of the same colour, it was quite difficult to tell in a split second which of the two rubbers had been used to serve the ball (there is a sound difference but everything is happening at split-second speeds).  The result was that a lot of service returns would be missed entirely or rallies would terminate with a seemingly inexplicable miss on the part of the receiver who didn't realize the "opposite" rubber was used to make the shot.  Rightly seeing this type of "trickery" increasingly affecting the outcome of matches and as being detrimental to the sport, the ITTF introduced the following "different covering colour" rule in 1983 which led to the red and black rackets seen in the sport today:

Rule 2.4.6: "The covering material on one side of the blade shall be bright red, and the covering material on the other side shall be black, whether or not both sides are used for striking the ball."

This is but one example of a rule introduced to ensure that changes in equipment or practices weren't detrimental to the sport.  There are numerous rules relating to equipment, facilities, play, etc..  From a player's or spectator's perspective, the rules are relatively straightforward.

See 'Table Tennis Rules' for more information 

The governing body for table tennis is the International Table Tennis Federation.  Among their many functions, they define and administer the Rules and Regulations.