What sets Java apart from other programming languages is the creation of the Java bytecode file by the Java compiler. In other languages, you write the source code, which is then converted into a low-level program. The Java compiler takes each class in the source file and converts them into Java bytecode files. The file extension for Java bytecode is ".class" to ensure that no matter what the operating system is, the Java bytecode is readable and run-able on any Java Virtual Machine (JVM), anywhere.
In other words, the Java compiler transforms the code you write into a readable version for the JVM to run and execute on your computer to accomplish exactly what you intended. It is an essential tool and will take you further into your Java learning and capabilities.