A package that is not intended to be used as a library. Application packages may have dependencies

A resource—Dart, HTML, JavaScript, CSS, image, or anything else—intended to be part of a deployed package. The package can be a web app, a package used by a web app, or any other package that benefits [..]

Another package that your package relies on. If your package wants to import code from some other package, that package must be a dependency. Dependencies are specified in your package’s pubspec

Entrypoint

A directory inside your package that is allowed to contain Dart entrypoints

A kind of place that pub can get packages from. A source isn’t a specific place like pub.dartlang.org or some specific Git URL. Each source describes a general procedure for accessing a package in som [..]

For more information, see Pub Assets and Transformers