Verbal irony is a rhetorical device that expresses a discrepancy between what is said and what is meant, in other words, it happens when we intentionally say things that we do not actually mean.
An example of verbal irony: Marks asked her sister Alice to wash his car, which he had lent her for a few days, and Alice agreed to do it. A few days later, however, Mark saw that the car was still dirty, he stared silently and then stared back to her sister and said: "Thank you for washing my car! I appreciate it very much. I will surely lend it to you next time you ask"
Did Mark actually mean what he said? The answer is no: he used verbal irony.