A new DEV Community article breaks down JavaScript's core mechanics: Execution Contexts, Hoisting, Scopes, and Closures. The JavaScript engine creates a Global Execution Context at startup and Function Execution Contexts for each call. During a context's Creation phase, the engine sets up the global object, initializes variables to `undefined`, and fully loads function declarations.

This setup explains Hoisting: variable declarations are processed before execution, why `console.log(name)` returns `undefined` for `var name = 'Tyler'`, but function declarations are available immediately. Function contexts manage local variables and the `arguments` object, with the single-threaded Call Stack pushing and popping contexts as functions execute.

Scope Chain determines variable accessibility, with the engine climbing from the current context outwards to the global object. Closures extend this power, allowing inner functions to retain access to their outer lexical environment even after the parent function completes, enabling patterns like factory functions and stateful modules.