The idea of a clone—a linked copy of an object that updates itself when the original changes—comes naturally from the vector way of thinking about graphics. You might say that a clone is not a real object—rather, it is just a command: “Display a copy of the object here.” The document stores that command, not an actual copy of the object. An actual cloned object exists only in the memory of an SVG application such as Inkscape when it loads the document.
There are both artistic and technical reasons to use clones. Watching several objects change live when you edit only one is in itself an exciting experience, opening many creative possibilities. On the other hand, using clones instead of duplicates makes the SVG document smaller and faster to display. Map symbols, repeated design elements such as bullets or icons, various symmetric designs or patterns—all these are easy to do with clones. Few other vector editors allow you to create live linked copies of objects with such directness and ease as Inkscape.