White space (also called negative space) is the empty area in a layout: margins, gaps between sections, padding inside a button. It is not wasted space. It is how the eye separates one idea from the next.
It is a tool of visual hierarchy, along with size and contrast. Crammed typography makes a page harder to scan, which hurts usability. The UI can be minimal and still fail if the gaps remove labels people need. Empty for its own sake is not the same as room to read. A design system usually names those gaps so every page breathes the same way.
A real-life example of white space
A Midtown accountant’s proposal stacks the fee against the signature line with no gap. Clients miss the number. The same page with a clear band of space above the total, and the total in heavier type, gets signed. Nothing new was added except room.
Leave space on purpose, around the thing you want noticed. When it goes too far: minimalism and white space. For the order of what people see: visual hierarchy.