Is there an echo in here???
The tools.jar files contains classes used by the JDK, classes that are not needed by the JRE. Examples include classes for things such as javac, javadoc, and many of the other executables found in the JDK bin directory.
As Jaikiran pointed out, that file should only ever exist in the JDK's lib directory and nowhere else (if you have several JDKs installed, each one will have its own copy). The version of tools.jar must match the version of the JDK and also the version of rt.jar (the primary JRE set of classes). This (making sure all of the versions match) is why it is important to set JAVA_HOME properly to the JDK installation directory.