Fluid grids are a dynamic approach to web design that adapts content layout based on the user's screen size and device. Instead of rigidly fixed dimensions, elements within a fluid grid are sized proportionally, allowing them to scale smoothly from large desktop screens to smaller mobile displays. This ensures a consistent and visually appealing experience across various devices.

Fluid grids are achieved through the use of relative units like percentages instead of fixed units like pixels. This responsive design technique helps prevent content from becoming cramped or stretched, creating a harmonious appearance no matter the screen size.