Peter :I usually scan as pdfs myself but can work with almost anything! If gifs are better, happy to get those!
Gifs keep line and edge detail but round the colour up to the nearest 256 colour (or greyscale) from a pallette and so they are ideal for compressing line drawings, text or business graphics, but no good for photos as 256 colours isn't enough for a realistic image. Jpgs decide upon a pixels colour by "averaging" the colours of the surrounding pixels (a simplification but similar) however the number of colours is not limited (within reason), this works great for areas of varying colour but blurs lines or edges and so is best for photos but no good for line drawings or text.
Generally speaking, you aren't learning much if your lips are moving.