p2 is the platform provisioning system used by the eclipse IDE and the eclipse RCP framework. It is an artifact and metadata repository and allows some kind of dependency resolution. it supports mirroring and has an extensive set of ant task for managing repositories and publishing artifacts. The eclipse IDE uses p2 to provision updates and install new plugins.
The Eclipse platform provides an installation and update mechanism called Eclipse p2 (short: p2). This update mechanism allows you to update Eclipse applications and to install new functionalities.
The update and installation of functionalities with p2 is based on feature projects (short: features) projects. It is possible to update complete products or individual features. In the terminology of p2 these features are installable units.