What is the purpose of using "breakpoints" in responsive design?

Using breakpoints in responsive design serves the critical purpose of changing styles based on the screen size. Breakpoints are defined points in a CSS stylesheet where specific styles can be applied or modified depending on the device’s width, height, or other characteristics. This approach enables developers to create a layout that adapts effectively across various devices, ensuring that the user experience remains consistent and visually appealing regardless of whether they are accessing the website on a mobile phone, tablet, or desktop.

By setting these breakpoints, developers can apply different CSS rules as the viewport changes, such as adjusting font sizes, rearranging elements, or hiding certain components to improve usability. This flexibility is fundamental in modern web design as it allows for a tailored experience that enhances readability and functionality across a multitude of devices.