Just-in-time compilation (JIT) is a technique used in computer programming to improve the performance of applications. Instead of translating code from a high-level language to machine code all at once before execution, JIT compiles code during runtime. This allows the program to optimize the code based on the current execution context, leading to faster performance. JIT is commonly used in environments like Java Virtual Machine (JVM) and Microsoft .NET Framework. By compiling frequently executed code paths, JIT can reduce the overhead of interpretation and enhance the overall efficiency of the application, making it more responsive to user interactions.