What is SVG?
Not pixels but instructions - shapes, paths and text that a browser draws at whatever size you ask for. That makes it perfect for logos, icons and diagrams, and useless for photographs. Converting an SVG to any other format here is the moment it stops being able to scale.
What is JPG?
JPEG is where photographs live. Its compression is lossy - it throws away detail the eye is bad at noticing, and throws away a bit more every time you re-save - which buys huge size savings on photos and makes a mess of screenshots and text. There's no transparency in it at all.