Most often prism is used to help with eye alignment/double vision.  When the two eyes are not pointed in the same direction then the brain receives two different images and interprets the world as being seen in double.  With compensating prism, we can bend the light traveling into each eye in a way that moves the images closer to each other to fix double vision.

Yoked prism is used to move the images of both eyes in the same direction.  Yoked prism is helpful for patients who have gaze palsies where both eyes can't look up or down - often due to conditions like brainstem stroke, restrictive strabismus (e.g., thyroid eye disease), nystagmus, abnormal egocentric localization, as well as cervical disorders of the neck that may cause patients to be unable to look in a certain gaze due to physical limitations of the neck's range of motion.  

There are many types of "field expansion" prisms including Peli Prisms, Gottlieb prisms, and yoked prism, which can be used for patients who have neurologic visual field loss like homonymous hemianopsia.  While this prism does not give patients their full peripheral visual field back, this prism can expand the field by 3-25 degrees which can help patients with things like reading, walking/ambulating in public​

Fresnel is a type of temporary prism sticker that can be used for patients who are unsure if prism will work for them and want to try it on their glasses first before buying it.  It can also be used for patients who only need prism for a certain gaze when they only get double vision when looking in a particular direction like left or down.