JPEG and JPG are the same thing. JPG could only be used in the past since earlier versions of windows only supported file extensions with three letters.
-lossy compression, which means smaller file size
-but can also mean a loss of image quality when scaled up
-good for everyday use
-does not support transparency
-lossless compression, bigger file size
-higher image quality, better text readability
-good for infographics, banners, screenshots
-supports transparency
-markup language to render 2D images within the browser, uses math, small file size
-can scale up infinitely without a loss of quality
-good for simple illustrations, icons, logos