From Unity 6000.3, Unity Search uses a single search index. By default, this index excludes packages, prefabAn asset type that allows you to store a GameObject complete with components and properties. The prefab acts as a template from which you can create new object instances in the scene. More info
See in Glossary content (indexes only prefab parent), and full 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 content. It also excludes properties that are common to all objects, or that for various reasons are never searched. You can add and remove properties from the exclusion list as needed.
To manage the index, refer to Search preferences reference.
You can also use custom indexers to give the Project (asset) search provider access to more properties. A set of custom indexers is available by default; to create more, refer to Create custom search indexers.
For more information, refer to the following resources: