Ok, lemme see if I can explain this, bear with me please.....
A gif consists of mulitple pictures (jpg's) that are stacked in layers and faded in and out to show an action or motion. There is a time delay between the frames (making a "frame rate") that can be adjusted to lengthen or shorten how long each individual frame is shown. You can also adjust the opacity (how "see through") it is, which will show or hide the next layer.
I've made a real quick .gif to demonstrate. I simply made the word "motion", with each letter being it's own layer. I put a small delay between the frames of .2 seconds to help space them out, and made it blink at the end.

In the program I use (Adobe Image Ready), it shows the frame, time delay and other things that you can adjust. I'll put a screen shot below of the .gif I made in Image Ready. In frame 1, the "M" appears for .2 seconds, then in frame 2 the "O" appears for .2 seconds, frame 3 shows "T" for .2 seconds so forth and so on. It's just a matter of showing and hiding different layers (jpg's) at different times, showing other layers (different jpg's) for different times, and having them placed so that it looks the way you want it to. I believe that you need a program to work with layers to create a .gif. I could be wrong, as I'm limited to using Image Ready.

Is this good, or would you like me to explain about layers (different pictures) and layer opacity (visability of a pictutre or layer) more?