Most logos are distributed vector-based. There are several vector-based file formats, such as EPS, PDF, and SVG. Simple images such as logos will generally have a smaller file size than their rasterized JPG, PNG, or GIF equivalent. You can read more about Raster vs Vector on the vector-conversions.com.
SVG or Scalable Vector Graphics is an XML-style markup-driven vector graphic rendering engine for the browser. Generally speaking, SVG offers a way to do full resolution graphical elements, no matter what size screen, what zoom level, or what resolution your user's device has.
There are several reasons why SVG is smart to store logo assets on your website or use it for print and paper collateral. Benefits including small file size, vector accuracy, W3C standards, and unlimited image scaling. Another benefit is compatibility — even if the facilities offered by SVG rendering engines may differ, the format is backward and forward compatible. SVG engines will render what they can and ignore the rest.
Having the 1-800 Flowers logo as an SVG document, you can drop it anywhere, scaling on the fly to whatever size it needs to be without incurring pixelation and loss of detail or taking up too much bandwidth.