Is this what you say when you're ready to go somewhere and someone's just standing around, for example?

Yes

And where is 'ARE' ?

Ah, when you mean “Let’s go!” you usually leave off the ARE.

What if I'm waiting for someone to come and they're not coming. Then I call them and ask: Ну ты идёшь?

In that case you ask: Are you coming?

🙏🤓

😉

Uly, in what situation can we say ”Are you going?”