Chimamanda Adichie is a highly-acclaimed writer from Nigeria; her books include Purple Hibiscus and Half of a Yellow Sun. The speech referenced was given at the 2009 TED conference, speaking about what she refers to as "The Danger of a Single Story." This refers to the commonality of Western fiction to write and read from a single cultural perspective; Adichie remembers having her early understanding of fiction informed entirely by these Western ideals, with white protagonists and Western issues. She had no understanding of the real cultural gaps between Western and Nigerian culture until her roommate at a U.S. college unwittingly treated her with condecension; Adichie refers to this incident as her first encounter with the "single story" of her homeland.
She had felt sorry for me even before she saw me. Her default position toward me, as an African, was a kind of patronizing, well-meaning pity. My roommate had a single story of Africa: a single story of catastrophe. In this single story there was no possibility of Africans being similar to her in any way, no possibility of feelings more complex than pity, no possibility of a connection as human equals.
(Adichie, "The Dangers of a Single Story," TED 2009)
When Adichie refers to the Single Story, she means the tendency of people from one country or region to stereotype other regions into popular catagories; she recalls doing the same thing when visiting Mexico. The danger of the Single Story is that it makes empathy difficult and understanding foreign culture almost impossible; it is easy to stereotype, but much harder to accept differences. Adichie entreats people to understand that there is never a Single Story for any place, but thousands of unique stories for each person living there, and people's amibitions, motivations, and characters are far more similar than one might initially believe, if based on the Single Story instead of on the truth.