Irony is the difference between what is being said and what is being meant.
English writer Anne Bradstreet used several instances of irony in her poems, mostly to mock society's assumptions as regards the role of women. For example:
"Who says my hand a needle better fits"
In the example above, Bradstreet refers to how society constrains women to do housework chores.
I would say that you would only use them when you are writing in the thousands or more other than that u don't use them
There was a booming knock at the door and a loud shout. " Open up! " From inside came the rattle of a lock, and then the door opened barely half an inch. A woman, dishevelled and clearly shaken, peered through hesitantly. " Can I help you? " Detective Stirland loomed large before her. He flipped his ID badge. " Where's Joe, Mandy? " " What's this about? " she stammered. Stirland applied his weight to the door and the woman stepped backwards as it swung open. " I'll ask the questions. We know he's here. " Her eyes flitted from his face to the lounge door and back. " Joe! " She folded her arms defiantly, reluctantly. " Joe, you'd better come out. The police are here. "
The answer is:- To show how slavery can destroy the deepest of human bonds.
Explanation— Frederick Douglas’ mother was not allowed to see him due to the laws given to them by their masters. He could only see her at night, because this was when she would sneak out to lie with at night. The practice of separating a mother and child by the slave master was a custom that was intended to break the natural bond of affection between mother and child.
I hope this helps.