Many people believe that chestnuts and ergots are vestigial toes that have migrated. Some believe they are vestigial scent glands. This latter theory explains why it's been said that you can carry the chestnut peelings of another horse into the paddock, and the horses there will come up to you to investigate, thus making catching easier. Has this worked for anyone? (I’ve never heard that, but now I want to try it!)
At any rate, chestnuts are on the inside of the legs above the knee and below the hock. They are kinda scratchy. Ergots are those pointy boogers on the back/bottom of fetlocks. However, while some horses have chestnuts and ergots, some do not.
Chestnuts also go by the name of "night eye.” Many people prefer to keep them flat and tidy; otherwise they can be a little lumpy and sometimes really pokey and long. The easiest way to keep them tidy is to peel them when they are wet. After a shampoo bath and rinse may be the best time to peel them.
Another option is to keep them oiled up with a baby oil or moisturizer and peel them after they are nice and soft. Some don't like the idea of using a blade or razor to remove them. In their eyes, they see this as a recipe for a disaster because you could either cut too deep, or have a squirmy horse wiggle into the blade.
Getting them soft and peeling has always worked for some. On show day, you can spiff them up with a coat of oil (like mineral or olive), or you can just let them be.
Ergots are also easily removed in the wash rack after a shampoo and rinse. Just use your fingernails. Please don't let them turn into kickstands as that could make things difficult.
So, how do you maintain your horse's ergots and chestnuts?