Just-in-time compilation (JIT) is a technique used in computer programming to improve the performance of runtime execution of applications. Instead of compiling the entire program before execution, JIT compilers compile code during runtime when it is needed, hence the name "just-in-time". This dynamic approach allows the compiler to optimize code based on runtime information, such as the types of data being used and the execution path of the program. This can result in faster execution times and more efficient memory usage compared to traditional ahead-of-time compilation. JIT compilation is commonly used in languages like Java, JavaScript, and .NET languages, where code is compiled to intermediate bytecode and then compiled to machine code during runtime. This allows developers to write code that is platform-independent while still achieving high performance.