Gif is usually a larger less pixelated file, this one takes 4 seconds to download. (56.6Kbs)
A smaller file which has more visible and larger pixels, an estimated 3 second download (56.6Kbs)
A Png-8 file is higher resolution the jpeg though a smaller file than a Gif and takes about 3 seconds to download. (56.6Kbs)
A Png-24 file Is the highest resolution of these 4, It takes about 6 seconds to download with small and smooth pixels. (56.6Kbs)