Some notes on terminology used in this help document.
  A frame is a single image in an animation. An ordinary bitmap image becomes a frame once it is inserted into an animation.
  An animation refers to the collection of frames, complete with all related timing and color instructions. A GIF animation defines a screen size which is the rectangle in which the animation is visible. Individual frames are clipped to this screen.
  A frame's delay is the amount of time that the animation pauses after displaying the frame and before displaying the next frame; the delay is the primary method of controlling the flow of the animation.
  A palette is a collection of colors that is used to define a frame. GIF animations can contain two different kinds of palettes: a global palette that applies to all the frames in an animation and a local palette that controls the colors of a single frame. The GIF format definition limits palettes to 256 colors.