Installer.app was a free software installer for the iPhone created by NullRiver and later maintained by RipDev, first released in summer 2007 and maintained until summer 2009. Installer allowed users to install third-party applications into the iPhone's Applications directory where native applications are kept. Users could install applications from a variety of sources (over WiFi or UMTS) provided by software developers, directly into the iPhone without requiring a computer. Users could browse lists of applications inside Installer to find ones they wanted to install. In June 2009, RipDev dropped support for Installer in favor of developing a different package manager and installer named Icy.
Read more about Installer.app: On IOS 2, On IOS 4 and 5