PNG

PNG stands for Portable Network Graphics

PNG is a bitmapped image format that employs lossless data compression.

The only bad thing about PNG is that it doesn't support animation, some good things that PNG can offer is the alpha channel which is capable of 256 levels of transparency, this allows you to create images that take any shape or form, PNG supports true colors up to 64-bits, gray-scale, and indexed colors, PNG images also have an automatic built-in cross platform gamma correction feature.

JPEG it is used for colour photographs, or any pictures with many blends and JPEG isn't good with sharp edges and tends to blur them.

GIF is best used for text, line drawing, screenshots, cartoons, and animation