When a site or app refuses SVG and also refuses PNG, JPG is what is left. JPG has no transparency, so a logo on a transparent background gets a solid one, and its compression can leave faint halos around hard edges. If the destination accepts PNG, PNG gives a cleaner result for vector artwork.
JPG has no transparency, so see-through areas of an SVG are filled with a solid colour, white by default; you can change it under Options. JPG holds a single still image, so an animated SVG does not stay animated. The defaults suit most files. Under Options you can set the quality, aim for a target file size, resize the result and set the scale the vector is rendered at.
The SVG is drawn at its own width and height (taken from its viewBox if it has no size) times the scale set under Options, scaled down if that would pass 16,384 pixels a side or 64 megapixels. Scripts inside the SVG never run and files it links to are not fetched, so text in a font the SVG does not embed is drawn in a fallback font.