Simple explanation
Submitting an app to the App Store or Play Store is not like uploading a file. There is a review process, and the reviewer is checking specific things: does the app crash on launch, does it have a privacy policy, does it do what the description says it does. Most first submissions fail on at least one of these. The rejection is not a verdict on your app — it is a checklist you did not know existed.
What to do
Before you submit, go through this list yourself: (1) Open the app on a real device, not a simulator, and tap every screen. If anything crashes, fix it first. (2) Make sure your App Store listing has a privacy policy URL — even a simple one. Without it, Apple will reject you automatically. (3) Read your own app description and ask: does the app actually do every single thing I said it does? If not, edit the description or add the missing thing. (4) Check that your app does not ask for permissions it does not use — camera, location, contacts. Reviewers flag these immediately. Submit only after you have done all four.
Copy-paste prompt
I am about to submit my app to the [App Store / Play Store] for the first time. Here is what my app does: [describe your app in 2–3 sentences]. What are the most likely reasons it could be rejected, and what should I check or fix before I submit?
Course note
Key takeaway
Test on a real device, add a privacy policy URL, and make sure the description matches what the app actually does. Do all three before you submit.