Explain the JavaScript event loop and task queues in detail.

Event loop enables async operations in single-threaded JS. Components: call stack (sync execution), Web APIs/Node APIs (async operations), callback queues. Macrotasks: setTimeout, setInterval, I/O, setImmediate (Node). Microtasks: Promise.then, queueMicrotask, MutationObserver. Loop cycle: execute stack, process ALL microtasks, render (browsers), ONE macrotask, repeat. Microtasks processed before next macrotask - can starve macrotasks. Node: additional phases (timers, poll, check). Understanding prevents: stack overflow, UI blocking, race conditions. async/await: syntactic sugar, still uses microtask queue.