Android is an open-source operating system used for mobile devices. It was developed by Android Inc., which was purchased by Google in 2005. Android is based on the Linux kernel and allows developers to write managed code using Java. The Android software stack consists of applications, an application framework, libraries and runtime, and the Linux kernel. Android uses security features like process isolation and permissions to protect applications and user data. It has many features like customization, notifications, app market support, and integration with Google services. However, it also faces limitations like inconsistent designs between apps, unstable performance, and lack of support for some Bluetooth functions.