The Java interpreter is a part of the JVM which translates Java byte codes into native machine codes and executes them.
An interpreter,provides a means by which a program written in source language can be understood and executed by the CPU line by line. As the first line is encountered by the interpreter, it is translated and executed. Then it moves to the next line of source code and repeats the process.
This means that:
The interpreter is a program which is loaded into memory alongside the source program
Statements from the source program are fetched and executed one by one
No copy of the translation exists, and if the program is to be re-run, it has to be interpreted all over again.