What is just-in-time or JIT compiler and what does it do?

Java uses javac (compiler) to convert the java code to byte code (.class file).

Then, JVM internally converts the bytecode to system understandable code using an interpreter in addition to it JVM.

Instead of executing a piece of code, again and again, JVM identifies them as “hot spots” and compiles them using Just in time compiler and, later reuses the same when required.