Reusing assets between projects

As you build your game, Unity stores a lot of metadata about your assets, 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 into one of these containers:

• A custom package, which you can access and manage inside Unity’s Package Manager.
• An asset packageA collection of files and data from Unity projects, or elements of projects, which are compressed and stored in one file, similar to Zip files, with the .unitypackage extension. Asset packages are a handy way of sharing and re-using Unity projects and collections of assets. More info
  See in Glossary, which you can create directly in the Editor.