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 dependency

A package that other packages will depend on. Library packages may have dependencies

A file named pubspec.lock

The declared versions of the Dart SDK itself that a package declares that it supports. An SDK constraint is specified using normal version constraint

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 [..]