okay, do they mean vectors, or tiles, because that's like saying "serving PNG JPEGs" or "serving JPEG PNGs". Some servers chuck back /a picture/, some servers chuck back /an SVG/ or line data.
You use a vector tile instead of a png or jpeg tile because you don’t want an image representation of the data, you want the raw “vector” data so you can style it, search it, and do other things with it on client devices.