GIF files can contain one of more GIF images. ANy photo, bitmap, paint, editor/program can edit a single-image GIF. But only programs that understand animation can properly edit a multi-image GIF. If you edit an animated (multi-image) GIF with a paint/photo/bitmap editor that has no animation capabilities you will likely only see the first frame of the animation and if you hit SAVE, the program will toss away all the extra images and convert it to a single-image GIF.