Fractint is a computer program that generates images of fractals. From version 5 through version 13, it saved images in a nonstandard extension of GIF format which we'll call FRA.
FRA files are standard GIF 87a files, except that they have additional fractal parameter data appended after what would ordinarily be the end of the file. They are compatible with most, but possibly not all, GIF viewers.
Later versions of Fractint use standard GIF 89a format, with fractal parameters stored in a GIF "application extension".