An animated GIF is just a series
of still images shown in sequences or layers. This is
a simple way to add animation to a web site that will
be displayed in the user's browser. This type of animation,
called GIF animation, or GIF89, was the first animation
to be used on the Internet which caught on and is
still widely used today.
GIF animations are incredibly
simple to work with and they are automatically recognizable
to most web browsers without the need for a plugin
to be downloaded. GIF animations can only contain
photos or graphics; they cannot contain sound.