Hello coders in the house and compliment of the season. I have a little problem on how mobile app are hosted apart from using services like aws , parse , and other mbaas.i really wanna know how to host app backend .like am I going to buy domain and host the db and the back end code there then integrate it with the app..thanks

You've already answered your questions. Read about restful api

JackOfAllTrades:
You've already answered your questions. Read about restful api

yeah thanks man but did you think let say whatsapp backend is hosted in a domain and from a particular url

That is the only way for all apps that connects to the Internet

so basically what you r implying now is that whatsapp has a website that is hosting it Erlang backend and database

Yes

Thank you very much man I appreciate..

You welcome

I agree with other members that you have already answered your question. In my opinion, mBaaS, IaaS, and PaaS platforms are the best to host mobile applications. If you want to explore anything in detail, then you should see these https://firebase.google.com/products-build Firebase products. These products tell everything in detail from database to hosting, authentication and notifications. They are also many videos available on YouTube to know how Firebase hosts the apps.

Although you have suggested a few back-end hosting services, you can also consider Kumulos and Back4App from this list https://blog.back4app.com/mobile-app-backend-hosting/ and explore their features. I favour Kumulos because it is a user-friendly platform where you can enjoy 30 days free trial. Back4App also gives good hosting for all kinds of apps with the support of Parse and MongoDB.