Android is a mobile device/operating system, that was created by Google.
Today, Android is one of the most used mobile devices. Because of this, hackers try to create malware for Android becuase of its larger market share. Some viruses on Android, are usually fake programs on Google Play. Android also has some ransomware viruses, but these function very differently than ransomware on PCs.
The latest version of Android is 7.1. Nougat.
There is a version in beta, called android O. Its release date is yet to be announced.