A jpg image (joint photographic project) type of image is purposely degraded (compressed) so that it's kilobyte size is small enough to send via email or place on a web page so the image doesn't take forever to load.  A jpeg image is usually low resolution  (number of pixels in an inch) and usually 72 pixlels/inch (because that's the resolution of computer monitors)

A tiff image is a format for printing.  You can't put tiff images on a website and it's not advisable to send via email because they are not compressed and very large (kilobyte size).  They are also higher in resolution (usually 300 to 600 pixels per inch) so that when they are printed, they are sharp and clear.

You can make either type of format (jpeg or tiff) out of a camera image using photoshop or other image software.  All computers come one.  On a Windows machine, it's called "Paint" and it's in the accessories folder of programs.  I'm not sure what it is on a mac.  Photoshop CE or Photoshop elements is the best.  For a more complete explaination, read the articles  about digital imaging and photography How To Articles .