What is a .svg file?

Your company logo is probably an SVG. You just never see the file. While JPGs and PNGs are grids of coloured pixels, an SVG is a set of mathematical instructions — draw a circle here, a curve there, fill it with this colour. The result scales from a favicon to a billboard without a single blurry edge.

SVG files are tiny (a logo that would be 50 KB as PNG might be 2 KB as SVG), searchable by screen readers, and style-able with CSS. They're XML under the hood, which means they're technically text files you can open in a code editor and modify by hand. That same openness is also a security consideration: SVG can contain embedded JavaScript, so opening files from unknown sources in a browser context deserves the same caution you'd give any script.

Every modern browser renders SVG natively. For editing, Inkscape is free and remarkably capable. Affinity Designer ($70) and Illustrator (subscription) are the professional options. SVG is the right format for logos, icons, illustrations, charts, and anything geometric. For photographs, it's the wrong tool entirely — use JPG or WebP instead.