SVG in the context of this article is scalable vector graphics that can be embedded in websites and displayed correctly in the browser.
What does “correct” mean?
— This is when you enlarge the page and the graphics are not blurred.
To clarify this, here's a picture that is saved in PNG (bitmap) and SVG (vector) + the word "buy". Now enlarge the browser window with Ctrl and + on Windows, or press Command and + on macOS:
buy — png icon (raster graphics)
buy — svg icon (vector graphics)
See how the first icon gets blurry?
Do you understand what the point is if a visually impaired user uses a browser with a magnification?
And then there are computers with Retina-screens, on which such icons will also be blurry.
If you don't want blurry icons, logos and other things, use SVG graphics.