conflict

Businessmen tug o' war in desert.
Andy Ryan / Stone / Getty Images

Definition:

Conflict is the heart of any plot. The conflict can be between the protagonist and another character, the antagonist; between the protagonist and nature; or the protagonist and society. It can also be an internal or psychological conflict.

While a conflict can be very straightforward: good versus evil, the best conflicts force a character to choose between two basically good outcomes.