Simple Definition:

Irony is a literary device that occurs when there is a discrepancy or contrast between what is expected or intended and what actually happens. It often involves situations that are surprising or amusing due to the opposite outcome than what was anticipated. Irony can be used to emphasize a point or create a humorous effect.

Example 1:
A fire station burns down. (unexpected outcome)

Example 2:
A person who claims to be an expert in healthy eating is seen eating a large pizza. (contrast between claimed expertise and actual behavior)

Very Simple Definition:

Irony is when something happens that is the opposite of what you would expect or think would happen.

Example 1:
A fire station burns down. (unexpected outcome)

Example 2:
A person who claims to be an expert in healthy eating is seen eating a large pizza. (contrast between claimed expertise and actual behavior)