I find myself using the word "texture" a lot these days when talking about games. I have used it in so many different contexts that I started to wonder if I was being consistent. For me, the concept of texture has many manifestations, but I think they are all related.
I specifically use the word "texture" because it evokes the image of a rough surface. The basic idea of texture is some form of disruption to the orthogonality of a game. In simple terms, a system is orthogonal if all of its properties exist for all other properties.
An example would be a lot full of cars. There are 4 different models of cars, in 3 different colors, having manual and automatic transmission. If all 4 models exist in all 3 colors and both types of transmission, the system is orthogonal. This is an over-simplification, but it serves my purpose.
Games with texture have something about them that breaks the smoothness of an orthogonal system. Each game and each turn does not feel the same. Furthermore, each players' decisions might not even feel the same. As with luck or weight, texture is not good or bad, but it is a factor in the game playing experience. So how does texture manifest itself?
One aspect of texture that applies to almost all games is that of players' playing styles. You can play a game two times--once with a passive opponent, and once with an aggressive opponent--and the game could feel very different. Games that specifically allow for extreme differences in playing styles permit this kind of player-induced texture.
Go, for example, is one of the most texture-less games; all stones are the same; all board locations are the same. Yet every game has different amounts and kinds of interaction.
Note that I consider playing styles to be the weakest kind of texture. There are much better ways to accomplish this as a design goal...
Some games create texture by having a random, player controlled, or scenario type setups. Not only might each game be different, but each player may have different advantages and disadvantages.
Examples of games with random setups are: Settlers of Catan (tiles), Caylus, Through the Desert, Tower of Babel, Around the World in 80 Days, and Rheinlander.
Examples of games with player setups are: Settlers of Catan (settlements and roads), Domaine, In the Shadow of the Emperor, and Keythedral.
Many games--particularly wargames--have scenario setups. This is one of the most extreme forms of texture. Each side usually has different numbers/types of units, strengths/weaknesses, positions, and objectives.
Some games create asymmetry during play using a random element: cards, tiles, dice. This may result in players needing to adjust their plans or completely abandon them. Events may occur which affect all players, but because of the various strategies, the affect may not be homogenous.
Examples of this are: Settlers of Catan, Euphrates & Tigris, Wallenstein, La Citta, and perhaps Friedrich.
The game board and other components themselves can be designed with texture. Spaces/cards/tiles can be different and/or limited. A piece on one space might have some unique advanatge. A player buying/owning a given card/tile may likewise get some unique advantage. In these cases tough decisions usually need to be made what to obtain and what to allow others to obtain.
Examples of these games are: Puerto Rico, Goa, St. Petersburg, and most games with an auction/bidding mechanic like: Princes of Florence, Amun-Re, and Ra.
As I was writing this, I pretty much came to the conclusion that all games have texture in one form or another. But some games I look at, and I see that texture was specifically intended...or at least added.
Settlers of Catan would be less interesting if the game setup was fixed. Tower of Babel would be less interesting if it weren't for the randomly placed discs. Puerto Rico would be less interesting if every player could buy every building.