Hypotheticals are situations, statements or questions about something imaginary rather than something real. Hypotheticals deal with the concept of "what if?"'. Grammatically, the term is a noun formed from an adjective, and the word is pluralized because it refers to the members of a class of hypothetical things.
Hypotheticals are very important because they provide a means for understanding what we would do if the world was different. Although this may assist our understanding of risk, and help us plan and create a new and better future, hypotheticals also help us understand the past, and why things happened or how things work. For example, in seeking to understand why a war started we could ask: "What if the parties had talked more first? Would they have worked out a better way of solving their problems? Could war have been averted?" Hypotheticals about the past are challenging to consider, as it is not possible to enter the past to change things according to our hypotheticals and determine what then may have occurred.
The philosopher David Lewis suggested in his book Counterfactuals (Blackwell Publishers, 1973) that when we use hypotheticals ("counter-to-fact-uals"), what we mean is: "In an imaginary world, exactly like ours, except in the one difference we are talking about ...". This idea is often called "possible worlds" and some people believe they actually exist, only we can't get to them, because the whole point is that they are different to our world.