I struggle to describe my depression in ways that will be make sense to me later (when I'm not depressed), let alone in ways that will make sense to other people.
When I was young (17, which didn't feel young at all at the time) I did not understand my depression at all, and was depressed to the point of contemplating suicide.
I was briefly medicated, but found that I disliked the experience. I felt like my emotions were 'flattened'. I'm sure anti-depressants are a good choice for many people, but I prefer living on a sort-of manic-depressive rollercoaster. I do my best to manage it, to see it coming and not put the people around my through hell by complaining about how depressed I am.
A lot of this might just be a function of my personality, of course.