V8 is Google's open source high-performance JavaScript and WebAssembly engine, written in C++. It powers modern web browsers like Google Chrome and is also used in server-side environments such as Node.js, among others. V8 supports ECMAScript standards and provides features like Just-In-Time (JIT) compilation, garbage collection, and WebAssembly execution. V8 is a critical component in enabling fast, scalable, and efficient JavaScript applications across various platforms.