Java runtime Enviornment

Java source files are compiled in the sense that they are coverted into a set of bytecodes from thetext format you write them.The byte codes are stored in .class file.At the runtime the bytecodes that make up a java program are loaded ,checked and run in an interpreter.In case of appplets you can download the bytecodess and then they are interpreted by Jvm in the browser.
Interpreter has 2 functions
-->Executes the bytecode
-->Makes appropriate calls to the underlying hardwarer