As you build your game, Unity stores a lot of metadata about your assetsAny media or data that can be used in your game or Project. An asset may come from a file created outside of Unity, such as a 3D model, an audio file or an image. You can also create some asset types in Unity, such as an Animator Controller, an Audio Mixer or a Render Texture. More info
See in Glossary, such as import settings and links to other assets, among other information. If you want to transfer your assets into a different project and preserve all this information, you can export your assets as a Custom Package.
See PackagesPackages are collections of Assets to be shared and re-used in Unity. There are two types of packages supported in Unity: Asset packages and packages available through the Unity Package Manager (UPM). Packages available through the Unity Package Manager are a fundamental method of delivering Unity functionality. More info
See in Glossary for detailed information on using Asset packagesA collection of files and data from Unity Projects, or elements of Projects, which are compressed and stored in one file, similar to Zip files. Packages are a handy way of sharing and re-using Unity Projects and collections of assets. More info
See in Glossary, including importing and exporting.
Use Export Package to create your own Custom Package.
HINT: When exporting a package Unity can export all dependencies
See in Glossary as well. So, for example, if you select a 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 and export a package with all dependencies, then all models, textures and other assets that appear in the scene will be exported as well. This can be a quick way of exporting a bunch of assets without manually locating them all.
Sometimes you may want to change the contents of a package and create a newer, updated version of your asset package. To do this:
Select the asset files you want in your package (select both the unchanged ones and the new ones).
Export the files as described above in Export Package, above.
NOTE: You can re-name an updated package and Unity will recognise it as an update, so you can use incremental naming, for example: MyAssetPackageVer1, MyAssetPackageVer2.
HINT: It is not good practise to remove files from packages and then replace them with the same name: Unity will recognise them as different and possibly conflicting files and so display a warning symbol when they are imported. If you have removed a file and then decide to replace it, it is better to give it a different, but related name to the original.