If you want to learn to work with Ionic then you should check out this links.
You have to get familiar with Angular since you will have to use alot of commands from it and its a very usefull/powerfull language.
->HTML (3rd Party site but explains things very well for beginners)<-
->CSS (same website from html)<-
Next thing is you have to understand how Ionic works.
As example one page has 4 Files in it.
.ts -> Typescript, for your coding
.css -> CSS, to style your Page.
.html -> HTML, to create buttons and other stuff what you need for your Page.
.module -> Modules, here you add modules.
So this is the first things you should know about ionic. The best way to learn how it works is to create a demo project.
First install ionic
npm install -g ionic cordova
After you typed in ionic start you should get a list with what you want to start with such as blank or tabs etc. Start with tabs and choose a name for your test app.
What you should do now is to check out how the app reacts if you change something in the app.component.ts or to the pages itself. Watch some youtube videos and read tutorials.
The key to understand Ionic is to test out many things and reading tutorials. Then you will also understand what the modules and native stuff is used for.
Good luck with your coding in the future!