Unity’s Package Manager

The Package Manager uses three interfaces to communicate with users, manifests, and registries:

• You can use the Package Manager window, which is the Package Manager user interface, to quickly browse and search for features. It also allows you to easily select the packages you want to install and update, and resolve conflicts in package dependencies.
• The Package Manager provides a dedicated Inspector in Unity, which allows you to walk through the contents of any package and view its manifest. This Project view integration means you can also edit package manifestsEach package has a manifest, which provides information about the package to the Package Manager. The manifest contains information such as the name of the package, its version, a description for users, dependencies on other packages (if any), and other details. More info
  See in Glossary directly in Unity for embedded or local packages.
• The Package Manager scripting API enables users to interact with the Package Manager programmatically.