Billiard balls are small, round spheres used in various cue sports like pool, snooker, and billiards. Typically made of resin or plastic, they come in different colors and sizes, with the standard pool balls being 2.25 inches in diameter. Each ball has a unique number or color, making it easy to identify during a game. When playing, players use a cue stick to strike the white ball, known as the cue ball, which then hits other balls on the table. The objective is to pocket the balls in designated holes, following specific rules depending on the game being played.