Browse each CSS unit to see its category and meaning, with a preview showing how a sample element renders so you can choose the right unit for your layout.
em is relative to the current element's font size, while rem is relative to the root element, making rem more predictable for global sizing.
vw and vh size elements relative to the viewport, ideal for full-screen sections and fluid typography that scales with the window.
Yes for fine details like borders, but relative units like rem improve accessibility because they respect the user's font-size settings.