Choose the size
An SVG is drawn from shapes, so it can be made any size without blurring; a PNG has a fixed number of pixels. The size menu draws each SVG at its own size, twice it (for high-resolution screens) or four times it, up to 8,192 pixels a side and 16 million pixels in all. The result names the size it was drawn at.
What an SVG may lose
Text in an SVG is drawn with the fonts on your device, so a font the file names but your device lacks is replaced. Images the SVG links to in other files are not loaded; images stored inside it are. An SVG with no size of its own is drawn from its viewBox, or at 300 × 150 if it has neither.
The new files are made in your browser from your images. Nothing is uploaded, and location and camera details (EXIF) are left out.