Responsive Design
In plain terms
Building web layouts that adapt to any screen size.
Going deeper
Responsive design uses flexible grids, fluid images, and CSS media queries so one site reshapes itself for phones, tablets, and desktops. It replaced building separate mobile sites.
Under the hood
Mobile-first CSS with min-width breakpoints, relative units (rem, %, vw), and modern layout (flexbox, grid); container queries now allow component-level responsiveness.
Examples
@media queries, Bootstrap grid, Tailwind responsive prefixes, fluid typography.
Think of it like...
Like water poured into different glasses: the same content reshapes to fill whatever container (screen) it lands in.