The iPhone OS platform was built using the knowledge that went into the creation of Mac OS X, and many of the tools and technologies used for development on the platform have their roots in Mac OS X as well. Despite its similarities to Mac OS X, you do not need to be an experienced Mac OS X developer to write applications for iPhone OS. The iPhone Software Development Kit (SDK) provides everything you need to get started creating iPhone applications.
An iPod is a portable device for storing and playing audio files encoded by MP3 or AAC compression algorithms. Designed by Apple Computer, iPods have distinctive styling and can hold anywhere from a few hundred to ten thousand songs
Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language.