Irony is best described as:

Irony involves a contrast between expectations and reality. When we describe a situation as ironic, we specifically refer to instances where the outcome is directly opposite to what one would anticipate. For example, if a fire station burns down, it highlights the ironic twist of fate since we would expect a place dedicated to firefighting to be safe from fire. This unexpected outcome creates a layer of meaning that can provoke thought, humor, or even a deeper commentary on a situation.

The other options, while they describe different literary concepts, do not align with the definition of irony. A detailed description of characters would focus on character development, a direct statement of facts is straightforward and lacks nuance, and an expression of certainty suggests a definitive stance rather than an unexpected outcome. Thus, the characterization of irony as a situation where the outcome is contrary to what was expected is the most accurate and fitting representation.