Uncertainty is only used to describe the uncertainty and instability of whether something will happen or not and the direction of change. That is, due to various factors: limitations of cognitive ability, limitations of information acquisition, and uncertainties of future things themselves, the stakeholders cannot calculate the deviation between the final implementation result of the project they are operating and the expected goal. For example, we spend two yuan to buy a lottery ticket, not sure whether it can win, the amount of this is uncertain, there is no loss and harm caused by the uncertainty, so there is no risk.