What are JVM and JIT?

JVM
JVM stands for the Java Virtual Machine. It is a virtual machine that runs Java programs and can be installed on several different operating systems such as Windows, UNIX, Macintosh etc. JVMs allow Java programs to run on almost any computer. A JVM processes instructions similar to a physical processor. However, the Java code (with "java" extension) must first be converted into Bytecode that the JVM understands.

JIT
JIT is the Just-In-Time compiler included in the JVM that compiles selected portions of the Bytecode into executable codes to improve the execution performance.