The extension .JAR refers to files of the type Java archive files. The java archive files are run by the run-time client of java, also known as the Java virtual machine.

The archive files on the client side can be directly run using a Runtime environment known as the Java runtime Environment(JRE). The JAR packages contain classes and interfaces that have the methods defined in them to execute the program. The JAR files can be used for one of the many flavours of java applications like Standard, enterprise, mobile or light versions. Jar files are popular for games and add ons on the mobile platform.