From Sedes Draconis
Tile games are a common past time of gnomes and some others. There are many different games of different levels of complexity that exist for a standard tile set.
A tile set consists of 105 tiles, each with unique faces, but indistinguishable by shape or back. Tiles are usually made of wood, sometimes bone, enamel, or cloisonné. They are thin, usually about .5cm thick, and trapezoidally shaped. The trapezoidal shape gives "top" and "base" edges which are easily distinguishable, which is important in some games. The top is around 2/3 as wide as the base and the two sloping edges are the same length as the base.
Each tile is the unique combination of three characteristics: shape, color, and number. There are 3 shapes, circle, triangle, and square; 5 colors, usually black, blue, green, red, white (the exact five colors used are one of the more variable aspects of a set); and the numbers 1 through 7.
So a tile face might depict four red circles or one black square, etc. These characteristics can be combined in 3x5x7 = 105 unique combinations, thus the number of tiles.