JIT compiler is a part of the runtime execution environment.
there are three types of JIT compilers:

1. Pre-JIT : Pre-JIT compiles complete source code into native code in a single compilaton cycle. This is done at the time ofdeployment of the application.

2. Econo-JIT: Econo-JIT compiles only those methods that are called at runtime.However, these complied methods are removed when they are not required.

3. Normal-JIT: Normal-JIT complies only those methodsthat are called at runtime.These methods are complied the first time they are called, and then they are stored in cache. When the same methods are called again, the compiled code from cache is used for execution.