Steps To Take When Building a Web App + An Ionic Mobile App

Hello world,

I have a new project coming up, and I’m little confused to the overall steps I will need to take. Originally, I was planning to build a web app on a Node stack and that would me done. However, I’m curious to try out Ionic, and since my app is a simple booking application, it looks like it could be a promising investment!

Do I build the web app as normal, then build the mobile app using the Ionic framework?
Or do I build the web app using the Ionic framework, and then build the the mobile app?

If the former, are there any special considerations I should take when making the web app?
If the latter, what are the key differences when building a web app using Ionic?

Sorry for my ignorance, I’ve read a few different resources but can’t wrap my head around it at present.

Thanks for any help,