system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The difference between diamond cuts and what makes one better than the other?
gpt
A lot of it is about light reflection. If you ask your mommy for a pocket mirror, you can put it near a lamp and make light reflect on the wall. When you move the mirror, light will do funny things and move on the wall. When you cut a diamond, something similar happens. If the pointy end of the diamond (the side that is hidden, under the ring) is too far away or too close to the top of the diamond (the pretty top you can see) it will reflect light in a way that does not look good. If you, look at the top, you will find that it is not shiny at all, and the people who buy them want them to be as shiny as possible. So you have to cut it exactly at the right place. Each time you make a little cut, which are the small shapes you see inside the diamond, you make a little mirror for light to bounce. If you meant cuts as in heart, pear and oval, you are talking about ''fancy cuts''. A lot of it is about the quality that your diamond has before it is cut. When you take it out of the earth, it is not always in a very good shape. Some people with big magnifying glasses look at it and decide if the shape and the shiny-ness is good enough. If it is very good, they will very likely cut it into the round brillant cut, which is usually the most ''ideal'' and popular form. The ''fancy cuts'' are a lot about fashion. Every few years or so, people start liking new things and that also affects jewelry, and diamonds. 
(I worked in a jewelry store, I've seen diamonds and pretty gemstones with lots of funky colors)