Space is the empty room between items on a page. Designers use it to keep words, buttons, and pictures from feeling crowded. Think of setting places at a table: leaving room between plates makes each place easier to see and use.
On a website, space might appear between a heading and its paragraph, or between two cards. It does not need to contain anything to be useful. The gap can show which items belong together and which belong to different sections.
If a page feels hard to scan, adding a little breathing room can help. Keep related things closer together than unrelated things, so the gaps quietly explain how the page is organized.