What changes during conversion
The image is decoded and rendered into a canvas, then encoded into the selected output format. This is not a filename-extension swap.
Transparency and JPG
JPG cannot store transparent pixels. When converting transparent PNG or WebP content to JPG, choose the background colour that should replace transparency.
Quality settings
JPG and WebP expose a meaningful quality control. PNG output is encoded without a cosmetic quality slider because browser PNG encoding does not use that parameter for lossy compression.