Answer
CSS3 is an informal name for the modular CSS specifications that followed CSS Level 2. • There is no single current “CSS3” specification containing all modern CSS. • CSS features now develop in separate modules with their own levels. • The CSS Snapshot describes the current collective state of CSS.
💡 Simple Example
@media (width >= 48rem) {
.layout { display: grid; }
}
⚡ Quick Revision
Modern CSS is modular; “CSS3” is a historical umbrella term.