Cascade layers are a new CSS feature that allows us to define explicit contained layers of specificity.

| elsewhere

A Complete Guide to CSS Cascade Layers

Repost from CSS Tricks

fragment of an inverted triangle with the cascade -- cascade layers are highlighted below element-attached styles and above specificity

We now have full control over which styles take priority in a project without relying on specificity hacks or !important. This guide is intended to help you fully understand what cascade layers are for, how and why you might choose to use them, the current levels of support, and the syntax.