Straw Man

An informal fallacy where you substitute a person's argument with a distorted, exaggerated, or misrepresented version in order to make it easier to attack. However, this tactic undermines a rational debate as one side of the discourse has had their argument deliberately distorted against their will. Thus, any conclusions reached from the discourse are rendered moot.

Logical Form

Person 1 claims A.
Person 2 restates Person 1's claim in an adulterated way and then attacks this misrepresented version.
Therefore, claim A is false.

Note, in practice, the individual committing this fallacy generally won't bother stating the new distorted claim before arguing against it. They will simply start attacking the new claim as if there's a tacit approval between the interlocutors that this is what was said. Further, misunderstandings are commonplace in arguments, debates, etc. However, it is important to stay vigilant during the discourse to make sure that distortions to your argument(s) aren't deliberate. If they are, then you are moving beyond the realm of misunderstanding to that of a logical fallacy.

Examples

Person 1: The science has shown that organically grown food is no more healthier for you than conventionally grown food [1].
Person 2: I didn't realize that you were so anti-organic. You're clearly too biased against organic to see its benefits.

Explanation: Clearly, just because Person 1 stated the science regarding organic foods and health doesn't automatically make them anti-organic. Additionally, even if you were anti-organic, this doesn't imply immediately that you're going to be so biased that you're immune to seeing any of the benefits of the practice. Person 2 has adulterated what Person 1 was saying in order to make the argument easier to dismiss as anti-organic nonsense.

Person 1: Due to the multitude of scientific evidence supporting evolution [2], there is no need for an intelligent creator or God when it comes to life.
Person 2: So you believe that we evolved from chimps? That everything you see around you is just some bizarre coincidence? That makes no sense!

Explanation: Here, Person 2 has intentionally exaggerated what Person 1 was stating about the theory of evolution in order to frame it as nonsense. Person 1 said nothing about humans evolving from chimps* or anything about the origins of the world around us. Person 1 was specifically talking about the theory of evolution and its implications on life.

*Humans did NOT evolve from chimps; however, we do share a common ancestor with them [3].

Person 1: Unequivocally, the Earth is round. Countless observations have been made along with countless measurements proving that the Earth is indeed round.
Person 2: You're not much of a free thinker are you? Your years of schooling, indoctrination as I like to call it, are clouding your judgment. Do you really believe NASA doesn't manipulate the images to suit their agenda? The Earth is definitely flat.

Explanation: Person 2 has distorted what Person 1 said to a degree that is almost laughable. Nowhere in Person 1's statement did he/she mention anything about NASA or the formal education system. The term “free thinking” is often used by individuals who embrace conspiratorial thinking in an attempt to rationalize holding a fringe view that is typically unsupported by any evidence. Person 2 has blatantly committed a straw man fallacy.

Person 1: The scientific consensus surrounding Global Warming is nearly unanimous among members of the scientific community. Humans, to a very high degree of confidence, are causing the Earth to warm. In fact, we now know that we're causing the Earth to warm at a rate that is 170 times faster than natural forces [4].
Person 2: So you don't trust our President then? Why don't you think he's doing a good job? I see no reason to distrust our President as the economy is doing so well [5]. As the President said, global warming is nothing more than a Chinese hoax [6].

Explanation: Person 2 is definitely committing a straw man fallacy here. Nowhere did Person 1 ever mention the President in his/her initial statement. Further, nowhere was it mentioned whether or not he/she had an opinion on whether the President was doing a good job or not. It is quite clear that Person 2 has deliberately vitiated the claims of Person 1 in order to dismiss his/her statement on the science of Global Warming and continue to believe that it's a Chinese hoax.

Conclusion

As always, if you find yourself confronted with this fallacy in everyday discourse, it is important to remember that it renders the argument bad and should be rejected. What is more, if you find yourself using this fallacy within one of your own arguments, as an individual who ascribes to the ethos of Critical Thinking, you must replace it with a good argument.