If you really want to understand, you'll just have to learn CSS. If you only care about doing quick prototypes, you can get by with a higher-level library like

If you really want to understand, you'll just have to learn CSS. If you only care about doing quick prototypes, you can get by with a higher-level library like material-ui, Bootstrap, etc. They tend to include their own simplified layout vocabulary, but you'll be dependent on that vocabulary's quality, documentation, and behavior, and won't realistically be able to step outside of it.