Image file types

Different file types are better suited for different image types.

GEEK SPEAK:
The main thing to consider is image compression. JPEGs can handle image compression whereas PNGs cannot. PNGs end up creating an index of every color used in an image. If you have an image that has a gradient or a wide range of colors all that data ends up being stored in the PNG image file causing the file to size to get really large really quickly.

The general breakdown is to use PNGs or GIF image formats for solid colors and to use JPEGs for TIFF image files for things like photos, or anything that has a gradient.