When some people think of depression, they think of that brief bit of heaviness they feel from time to time, the sadness that makes you want to cry, and that feeling of hopelessness that makes you wonder if the world will ever be okay again. And sometimes it is. Sometimes our depression is heaviness and hopelessness and sadness, but depression is so much more.
The term "depression" is almost an umbrella term for all of the different depressive disorders. You can say that you have depression and be telling the truth without telling them what type of specific. There's so many different forms of depression; there are even more different ways how everyone experiences depression.
Non-Clinical Depression (Situational Depression)
This is the kind of depression that gets talked about callously, and it's mainly situational depression rather than clinical depression. Because some people say they're depressed when they're not. That can make people with diagnosed depressive disorders feel like anyone without a diagnosed depressive disorder doesn’t have “real depression.” On one hand, it might not be, but on the other hand, it could be. The real push pull here is that it's essentially like a minor depressive disorder because it wasn't "big" enough to get the attraction of someone who could spot a problem with it. Keep in mind: Sometimes depression isn't diagnosed because people don't know that it's an issue. But sometimes people say they're depressed because they can get attention for it. Whether or not you take the person seriously about their depression depends on you and your view of that person, but that's the summary of what happens around non-clinical (a.k.a. non-disordered depression).
Dysthymia
To put it quite simply: minor depressive disorder. But basically, you're feeling the same types of depression as you would with situational, just it's persistent and has no real reason other than the upset of chemicals in your brain.
Major Depressive Disorder
This one's fairly self-explanatory. The depression here is more intense than it would be with dysthymia. You may feel incredibly hopeless, even to the point of being an incredible danger to yourself and your well-being.
Seasonal Affective Disorder
When I try to summarize this one, what basically comes to mind is that it's a depressive disorder where your depression is primarily influenced by how much sunlight you get. Think of it as if you're a plant, but instead of needing sunlight for food, you need it in order to thrive emotionally.
Bipolar Depression (All Types)
Bipolar, put simply, is a disorder of mania (or hypomania) and depression, where you bounce back and forth between the euphoria of mania and then emotionally collapse into the pit of deep depression (Hypomania is a lesser form of mania).
IMPORTANT NOTES
If you or anyone you know may be at risk of hurting themselves or others, whether due to a depressive disorder or otherwise, PLEASE seek help. Depressive disorders can drive you down into deep pits of internal darkness, to the point where we may lose any sense of control over what we think or do. If you think someone is at risk, do not hesitate to contact someone who may be able to help. Siblings count, but try to get a responsible adult to be involved too. Hopefully it won't be needed, but here's the suicide lifeline should you wish to note it down:
Suicide Lifeline (Call & Text) - 988