Success!

I've been thinking a lot about what a dice roll really means within a role-playing game. What it is meant to convey and how it is applied are usually two different things. Dice usually means risk of failure, not just chance of success. If there is a risk that something bad could happen then the dice come out, or if there's a chance that something really good could happen the dice come out. Or both.

Consider a player who says "I want to climb a nearby tree and try to get a better look at this valley."

GMs would handle this request differently, some might require a roll, and some might just let the PC climb a tree and draw a crude map without a roll. I'm going to focus on GMs who require rolls, and what that roll would mean.

First, there is a simple question of success or failure. Success is "you climb the tree" and failure is "there are no decent handholds, you don't climb the tree."
GURPS uses this method, though it also uses a complex skill system to determine where that success is achieved.

Second there is the chance of extra benefit or complications. Extra benefit might be "you climb the tree and make a rough map quickly and efficiently" and complication might be "you fall out of the tree and take some damage."
In D&D, and many of it's variants, this is frequently represented by rolling an unmodified result of '1' or '20'

This is usually where most dice rolling conventions end. But there's additional possibilities within the dice roll.

Consider the partial success, which I enjoy using. A partial success might be "you can climb the tree and make a map, but there is no safe way down and you'll have to fall most of the way" or "if you climb the tree, you'll expose yourself to pterodactyls circling overhead" or "you can only make it halfway, the branches above are thin and weak, if you climb any farther you risk breaking the branches and falling to the ground."
Apocalypse World explicitly uses the partial success.

Then there's extending the outcomes into an exacting range of "success with extra benefit," simple "success," "success with complication," "failure with extra benefit," simple "failure," and "failure with complications."
Venger Satanis' VSd6 system accomplishes this.

The results and methods of achieving them are diverse. The results however are almost always determined by the GM. The players drive the action forward but the GM lays down the roads that they follow. I think the best players are the ones who forget the roads exist, and that the best GMs are the ones who say "Where we're going, we don't need roads."