Here is a brief explanation of what is involved.
Scenarios are a way of thinking about the future.
They were developed within the corporate world by business strategists concerned with the weaknesses of existing approaches to planning. One of the dangers in traditional planning is that it usually relies on a forecast of future conditions based partly on the past and partly on expected changes which should impact on the future. The problem arises that most forecasts are wrong and therefore strategies based on them are likely to be at least partly flawed. Scenario planning takes an alternative approach. In considering a good scenario, it is best to begin with what they are not.