Technology giant Apple said more than 15 billion applications have been downloaded from its App store and paid over $2.5 billion to developers.

App Store offers more than 425,000 apps, out of which over 100,000 apps is exclusive for iPad.

The App Store, which is accessible from the iPhone, iPod Touch and iPad via an iOS application by the same name, is one of the key success factors of Apple's devices such as iPhone and iPad as it provides a complete ecosystem. The same factor helps the user to stick to Apple.

In just three years, the revolutionary App Store has grown to become the most exciting and successful software marketplace the world has ever seen, said Philip Schiller, Apple's senior vice president of Worldwide Product Marketing, in a statement.

Cupertino, California-based Apple has over 200 million iOS users using iPhone, iPad and iPod touch.

The App Store, which opened in July 2008, is a digital application distribution platform that allows iOS users to browse and download applications from the iTunes Store. Depending on the application, they are available either for free or at a cost. The applications can be downloaded directly to a target device, or downloaded onto a PC or Mac via iTunes.

Generally, Apple retains 30 percent of the revenue from the store, while the balance 70 percent goes to the developer. The App Store is also accessible through iTunes, and then on any iTunes-supported operating system such as Mac OS X and Windows.

In October 2010, Apple unveiled the Mac App Store which was eventually launched on January 7, 2011.

After the success of Apple's App Store, Apple applied for a trademark on the term App Store in 2008, which was tentatively approved in 2011. Later, Apple sued Amazon for using the term Appstore for its online store of apps.

However, on July 6, a California court denied Apple's motion for a preliminary injunction on Amazon.com's use of the term Appstore.