What are CSS frameworks?

What are CSS frameworks?

A CSS framework is a software framework that is meant to allow for easier, more standards-compliant web design using the Cascading Style Sheets language. Most of these frameworks contain at least a grid.
Some common frameworks include :
Bootstrap
Foundation
Bulma
Ulkit
Semantic UI

A CSS framework is a software framework that is meant to allow for easier, more standards-compliant web design using the Cascading Style Sheets language. Most of these frameworks contain at least a grid. More functional frameworks also come with more features and additional JavaScript based functions, but are mostly design oriented and unobtrusive. This differentiates these from functional and full JavaScript frameworks.

Two notable and widely used examples are Bootstrap and Foundation.

CSS frameworks offer different modules and tools:

reset style sheet
grid especially for responsive web design
web typography
set of icons in sprites or icon fonts
styling for tooltips, buttons, elements of forms
parts of graphical user interfaces like accordion, tabs, slideshow or modal windows (Lightbox)
equalizer to create equal height content