Explain the concept of the "Lost Generation" in F. Scott Fitzgerald's The Great Gatsby.
To expand on mary648's response, the term "Lost Generation" was coined by poet/writer Gertrude Stein. It is often used to refer to American expatriot writers living in Europe (specifically Paris) during the 1920's, including Fitzgerald, Hemingway, John Dos Passos et. al. The phrase really grew out of the devastation following World War I. So many millions of young men were killed and maimed in the first mechanized war in human history. World War I challenged traditional value structures and raised new questions of morality. Remember, in Chapter One, Nick is seeking a world at a sort of moral attention (my paraphrase) and Gatsby represents someone who possesses those old-world values (mainly romantic idealism). So, in many respects, an entire generation of men were lost, literally killed in war (how many potential artists, writers, doctors, teacher,etc. were killed?) and those that remained had the values and ideals that they grew up with ripped away from them.
The "Lost Generation" was a name given to the generation that was young (like in their 20s and 30s) during the 1920s. The generation was given this name because people said that they were lost in terms of having no focus in life and no real values. You can totally see this in the characters in The Great Gatsby.
Think about Jordan and Daisy for example. They seem to float through life with not goal or purpose. The same seems to go for the people who come to Gatsby's parties. The people are just there because it seems like the thing to do. They all seem so shallow.
By portraying people with no goals and no values, Fitzgerald is showing that he believes that this really is a "lost generation."