If I want to change something in my app, does it have to go back to Apple and Google before my customers see it?
Sometimes yes and sometimes no, and the difference is where the thing you are changing actually lives. Content that the app pulls from your portal, such as your offers, banners, package descriptions, markups, search settings and most text, changes the moment you save it, because the app is simply asking your system for the latest version each time it opens. Your customers see that straight away with nothing to download.
Anything built into the app itself is a different matter. A new screen, a change to how the booking flow works, a new payment method, a new icon or a fix to something that behaves badly on a particular phone all sit inside the app file, and a new version of that file has to be submitted to Apple and Google. Both stores review what you send before they let it out, and the wait varies from a day or so to longer if they come back with questions.
Even after the store approves it, your customers do not all move over at once. Phones set to update apps automatically will pick it up over the following days, and anyone who has automatic updates switched off stays on the old version until they choose to update, so for a while you have people using two different versions of your app.
Before you plan anything with a date attached, such as a campaign or a new payment option, check whether it is a content change or an app change, and if it is an app change give yourself room for the store review and for customers to update.
