Cannabis can be used for a number of ailments including nausea, anorexia, movement disorders, pain, glaucoma, epilepsy, asthma, dependency and withdrawl, autoimmune diseases and inflammation, and all sorts of psychiatric symptoms.
Edibles are just a different way of ingestion. I don't like the high it gives anymore so when I take it for pain and inflammation I choose to eat it, makes me feel less "high". Now that many states in the US have made recreational and medical use of cannabis legal, labs are free to text and experiment with different combinations of the two most prevalent drugs in cannabis: THC and CBD. THC is what gives you the high, CBD is what helps with the inflammation. Sometimes I take 100% CBD products which means I get absolutely zero high whatsoever but I still get rid of the inflammation.