The magnification determines image scale. 50X makes the object appear to be 50X nearer to you and hence 50X larger than as seen by the unaided eye. This is independent of the field of view. Whether the eyepiece is a narrow or a wide field design, the apparent size of the object, or some part of it, on your retina will be the same.

The eyepiece design determines whether it delivers a narrow, moderate or wide field. When you peer into an eyepiece, the image is framed by a (nominally) sharp-edged circle of blackness. The apparent angular diameter of this circle on your retina sets the apparent field of view (AFoV). As the AFoV gets wider, the view looks like you are getting closer to a porthole on a spaceship. For instance, an ultra-wide AFoV of 100° appears 2X wider than the standard 50° AFoV, and because area is a squared function, covers 4X more area. It's like the difference between a basic cinema screen and IMAX.

The true field of view (TFoV) depends on both the magnification and the AFoV. For instance, if a 50X eyepiece has a 50° AFoV, it's TFoV is 50° / 50X = 1°. By comparison, a different eyepiece delivering the same 50X eyepiece but having a 100° AFoV (twice as wide an image circle) will provide a TFoV of 100° / 50X = 2°.

Note that in the foregoing both eyepieces deliver the same 50X, meaning the image scale will be the same, the amount of detail will be the same, and the image brightness will be the same. The principal difference will be the factor of 2 difference in both the AFoV and the TFoV, and the 4X difference in sky area and retina covered with imagery. The wider AFoV at given magnification covers more sky, thus permitting to accommodate larger objects, and it makes panning about or star hopping more efficient. And it better exploits the more sensitive outer retina. And it makes for a more immersive viewing experience.

Consider an eyepiece of 25mm focal length and AFoV of 50°. Now consider an eyepiece of 12.5mm focal length and AFoV of 100°. The second eyepiece, having 1/2 the focal length of the first, will deliver 2X the magnification. But it has 2X the AFoV, compensating for the doubled power, hence resulting in it still providing the same TFoV as the lower powered eyepiece.