Factor of Safety is a ratio of the limit of the material or project to the current situation of loading that it experiences. The limit is defined as the maximum amount of loading the material/project can experience before it starts cracking or deforming that leads to failure. Current Situation is the amount of loading that it is experiencing right now, loading as in amount of forces on it.
This is important because we always want the Limit to be greater than the current situation. If it was reversed, then the project is highly at risk for failure, therefore not a wise design choice
For example, the Golden Gate Bridge has a Safety Factor of 6, which means that its limit is always around 6 times greater than what forces it actually experiences. These forces come from the combined weight of the thousands of cars that drive on the bridge. Here’s an additional source where you can see the Factor of Safety of real projects that include bridges, engines, aircraft parts, and so on:
