React/Chakra or bootstrap

Hi dears

I am learning react with Mosh and this is the first time i wanna use chakra for styling the code
before that i used bootstraps and for that I dont have any index.css and app.css
but for chakra Mosh said in the video that just put within
and I dont get that. what is the role of index.css and App.css in this process?

If you’re using chakra only and without custom css styles then index. css and app. css is useless to you. But if you want to add some custom css styles on your project then you should write them on index.css and include it on the app. tsx

Summing up
index. css and app. css in your react with chakra project if for applying custom css that you think it’s impossible to write them in chakra.
But if you’re using chakra only then you don’t need both of them