A counterclaim is an argument or position that rebuts another argument or position. Within the context of To Kill a Mockingbird, one might advance the argument that Atticus Finch had to defend Tom Robinson because of his strong sense of morality and his need to set an example for his children and the townspeople of Maycomb, Alabama. The counterclaim to this argument would be that Atticus Finch should not have defended Tom Robinson, as in doing so, he put himself at odds with the racist community in which he lived and jeopardized the well-being of his children. In creating a counterclaim, a writer must address the other side of the argument he or she plans to make in an essay.
Making a claim is just a fancy way of saying that you're stating your main point. A claim tells what you think is true about a topic based on your knowledge and your research. 'Mom, I really need a new cell phone!' If you've ever said this or something like it, you've made a claim. In a formal paper, you might say something like, 'It is necessary for me to obtain a new cell phone.'
But there are two sides to every argument. In your argument for a new cell phone, your Mom stands on the other side. She has something to say against your claim that you need a new cell phone, and it goes something like, 'No, you don't.'
That's your mom's counterclaim. A counterclaim is just the opposite of a claim. In a more formal way, she might say, 'Your current situation does not require a new cell phone.' Counterclaims are also provable and supportable by reasons and evidence. Not just, 'Because I said so.' When you're planning an argument, you need to know what the counterclaim might be so that you can make sure that you disprove it with your reasons and evidence