A package contains features to fit the various needs of your project. This can include any core features of Unity which is installed along with the Editor, or other packages which you can install as needed.
For more information about using packages in general, see Unity Package Manager.
If you are only interested in finding documentation or information about a specific package, click the links on the Verified and Preview packages and Built-in packagesBuilt-in packages allow users to toggle Unity features on or off through the Package Manager. Enabling or disabling a package reduces the run-time build size. For example, most Projects don’t use the legacy Particle System. By removing the abstracted package of this feature, the related code and resources are not part of the final built product. Typically, these packages contain only the package manifest and are bundled with Unity (rather than available on the package registry).
See in Glossary pages. To find a package by keyword, see the Packages by keywords page.