There are a lot of articles, some really good but I read through two of CSS-tricks articles and that is all there is.
Besides the already mentioned css-tricks articles, I recommend checking out the guide to flexbox from mdn[1] (in the side menu there is also one for grids) as well as the reference to “CSS flexible box layout”[2]. These helped me get a deeper understanding about the concepts behind flexbox and how the properties and their shorthands actually work.
[1]: https://developer.mozilla.org/en-US/docs/Learn/CSS/CSS_layou...
[2]: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_flexibl...
They were conceived to float text (or other elements) around static elements. Think text floating around a picture, like this:
https://tco-forum-uploads.s3.amazonaws.com/original/3X/0/3/0...
Some consequences of that are that you can easily adjust the order and such. And just need to change one elements style to adjust the whole layout.