I feel like I have the same preconceived idea as anyone else when it comes to knowing what Tragedy is. It's a work of literature that deals with a story that has a character, usually a main character, experiencing a sort of loss or any devastating event that changes the whole shtick of the character for the whole story. Or, if the event happens at the end of the story we as readers can easily assume that the event will surely change how the character acts outside of the confines of the story itself.
So after researching it more on Wikipedia, I found that Tragedy is generally a story about human suffering that provokes a sense of catharsis or sensation, depending on the reader. So this definition just basically confirms my first thought of what Tragedy is. Except for the fact that it states how it gives the audience or reader a sense of catharsis or sensation.