A misconception resulting from flaw in reasoning, or a trick or illusion in thoughts that often succeeds in obfuscating facts/truth.
A formal fallacy is defined as an error that can be seen within the argument's form. Every formal fallacy is a non sequitur (or, an argument where the conclusion does not follow from the premise.)
An informal fallacy refers to an argument whose proposed conclusion is not supported by the premises. This creates an unpersuasive or unsatisfying conclusion.
Logical fallacies are errors in reasoning or argumentation that can undermine the validity of an argument. They are often used to mislead or distract from the truth, or to win an argument by appealing to emotions rather than reason. It's important to be aware of these fallacies in order to critically evaluate arguments and avoid being misled.
A few books to help you get a real handle on logical fallacies.