Unity categorises most save information into Scene changes and Project-wide changes.
Note: An exception to this behaviour occurs when you edit in Prefab Mode. In this case, File > Save only saves changes to the open Prefab. It does not save Scene changes or Project-wide changes.
Unity also saves some information immediately while you’re working in the Editor. See Immediate saving, below, for more details.
Scene changes include modifications to GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary in the SceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary, such as when you:
Project-wide changes in Unity apply to your whole Project, rather than a specific Scene. If you want to save Project-wide settings without saving Scene changes, go to File > Save Project. You might find this useful if, for example, you create a temporary Scene to test some changes.
Project-wide changes include:
There are some changes which Unity immediately saves to disk when they happen. These include the following: