The JavaScript event loop execution order, summarized in a simple manner

The simplified order

1. Everything in sync
2. Microtask queue
3. Task queue

Real-world examples

Tasks

setTimeout, setInterval, setImmediate, ...

Microtasks

Promises, queueMicrotask, MutationObserver, ...

Everything combined

// Schedules a new microtask
queueMicrotask(() => console.log("microtask"));

// Schedules a new task
setTimeout(() => console.log("task"), 0);

console.log("main");
// Output order: main, microtask, task

Please note that this describes a really, really simplified perfect-world case. If you would like to find out more, I can highly recommend Jake Archibald's blog post on this topic.