The document provides an overview of the Java Native Interface (JNI) including: - JNI allows Java code to call methods of native libraries written in other languages like C/C++. - It separates Java code from native code to allow Java to reuse existing native libraries and enable access to hardware-level services. - The process of creating native methods using JNI involves writing Java and C/C++ code along with a JNI interface file to link them.