SVG
A scalable vector graphic format that preserves sharp edges at any output size.
In practice
SVG is an open file format for vector graphics, written as readable text that describes shapes, paths and colors. Because browsers draw it directly, an SVG icon stays sharp on any screen, can be recolored with code and is often smaller than an equivalent pixel image. It suits logos, icons, charts and simple illustrations, but not photographs. The menu icon in a website's corner is a typical SVG.
Often confused with Vector File
Vector file is the general category of path-based images; SVG is one specific, web-friendly vector format among several.
Try this
Open a simple SVG icon in a text editor, change one color value, and reload it in a browser.