Fixed websites have a set width, and resizing the browser or viewing it on different devices won’t affect on the way the website looks. This can require horizontal scrolling and a site that doesn’t look good on tablets or smartphones.
Fluid websites are built using percentages for widths. As a result, columns are relative to one another and the browser, allowing it to scale up and down fluidly.
Adaptive websites introduce media queries to target specific device sizes, like smaller monitors, tablets, and mobile.
Responsive websites are built on a fluid grid and use media queries to control the design and its content as it scales down or up with the browser or device.