See page 4, the "characteristic curve" for FP4 is low and right. The shape of this curve is called an "S" shape.
The area where the low end of the curve turns upward, by the #1, is the toe; this is the dark end of the photo. At the top of the curve where it flattens, about 3.5-4, is the shoulder; the highlight end of the scale.
Compare that to Kodak TXP. Page 14.
TXP has a much longer toe and little if any shoulder. This is called an upswept curve.
The shape of the curve changes how the photo prints. Each film has a unique curve and different developers and other changes can also change the shape of the curve as can time and other changes.
(One is not "better" than the other, they are simply different tools. Both of these films are truly special and beloved by many.)