Android is an open-source operating system developed by Google and the Open Handset Alliance. It uses a Linux kernel and allows developers to write applications using Java programming languages that run on the Dalvik virtual machine. Some key features of Android include customization options, multitasking capabilities, an open application framework, and integration with services like maps, email and web browsing. While openness allows for customization, it also presents security risks from hacking. Android competes with Apple's iOS and differs in features like customization and multitasking support.