Tennis is a sport usually played between two players (singles) or between two teams of two players each (doubles). Each player uses a racket that is strung to strike a hollow rubber ball covered with felt past a net into the opponent's court.The modern game of tennis originated in the United Kingdom in the late 19th century as "lawn tennis" which has heavy connections to various field/lawn games as well as to the ancient game of real tennis. After its creation, tennis spread throughout the upper-class English-speaking population before spreading around the world.Tennis is an Olympic sport and is played at all levels of society at all ages. The sport can be played by anyone who can hold a racket, including people in wheelchairs.The rules of tennis have not changed much since the 1890s. Two exceptions are that from 1908 to 1960 the server had to keep one foot on the ground at all times, and then the adoption of the tie-break in the 1970s. A recent addition to professional tennis has been the adoption of electronic review technology coupled with a point challenge system, which allows a player to challenge the line (or chair) umpire's call of a point.Tennis enjoys millions of recreational players and is also a hugely popular worldwide spectator sport, especially the four Grand Slam tournaments (also referred to as the "Majors"): the Australian Open, the French Open, Wimbledon, and the US Open.Equipment :Part of the appeal of tennis stems from the simplicity of equipment required for play. Beginners need only a racquet and balls.Racquets -The tennis racquet comprises a handle and neck joining a roughly circular frame that holds an array of tightly pulled strings. For the first century of the modern game, racquets were of wood and of standard size, and strings were of animal gut. Laminated wood construction yielded more strength in racquets used through most of the 20th century until first metal and then composites of carbon graphite, ceramics, and lighter metals such as titanium were introduced. These stronger materials enabled the production of oversized rackets that yielded yet more power. Meanwhile technology led to the use of synthetic strings that match the feel of gut yet with added durability.Balls-Tennis balls are of hollow rubber with a felt coating. Traditionally white, the predominant color was gradually changed to Optic Yellow in the latter part of the twentieth century to allow for improved visibility.Miscellaneous-Advanced players improve their performance through a number of accoutrements. Vibration dampers may be interlaced in the proximal part of the string array for improved feel. Racket handles may be customized with absorbent materials to improve the players' grip. Players often use sweat bands on their wrists to keep their hands dry as well. Finally, although the game can be played in a variety of shoes, specialized tennis shoes have wide, flat soles for stability and a built-up front structure to avoid excess wear.