A promise is a value, not a callback

Callbacks invert control: you hand your code to someone else and hope they call it once. A promise gives you back a value representing the eventual result, and values compose. You can put promises in an array, pass one to two different consumers, kick one off now and await it three functions later, or return one from a function whose caller decides when to care.

async/await is syntax over that value. An async function returns a promise the instant it hits its first await, and the rest of the body is scheduled as a continuation on the microtask queue. That is the entire mechanism, and it explains the two behaviours people find surprising: an async function with no await still returns a promise, and awaiting a non-promise still defers to the microtask queue.

The habit worth building is separating starting from awaiting. const a = fetchA(); const b = fetchB(); const [x, y] = [await a, await b]; runs both requests concurrently, where awaiting each at its call site runs them one after the other. Same-looking code, twice the latency. This distinction is the difference between understanding promises and reciting them.