JIT Compilation
In plain terms
Compiling code to native form at runtime for speed.
Going deeper
Just-In-Time compilation translates bytecode or scripts into machine code during execution, optimizing hot paths on the fly. It blends interpretation and compilation.
Under the hood
Profiles running code to optimize frequently-used paths; powers fast JVMs and JavaScript engines.
Examples
JVM, V8 (JavaScript), .NET, PyPy, runtime optimization, hot paths.
Think of it like...
Like a translator who, noticing repeated phrases, memorizes them for instant future translation.