Chillingeffects.org wrote:

Question: What is the difference between libel and slander?

Answer: Libel is a defamatory statement expressed in a fixed medium such as a writing, picture, sign or electronic broadcast. Slander is a defamatory statement expressed in a transitory form such as speech.

Question: What is the legal definition of defamation?

Answer: The elements that must be proved to establish defamation are: (1) A publication to one other than the person defamed; (2) of a false statement of fact; (3) which is understood as being of and concerning the plaintiff; and (4) which is understood in such a way as to tend to harm the reputation of plaintiff.

Question: Does it make any difference if I am commenting on a product or company rather than a person?

Answer: Product disparagement law prohibits certain false claims about another's goods or services. While a defamatory statement harms the reputation and character of a person or corporation, a product disparaging statement harms the marketability of the goods being disparaged. Product disparagement is typically harder to prove.

Question: What is false light invasion of privacy?

Answer: "False light" is a claim that publicity invades a person's (plaintiff's) privacy by a false statement or representation that "places the plaintiff in a false light that would be highly offensive to a reasonable person."

Question: What is the difference between false light invasion of privacy and defamation?

Answer: The distinction between the two is a subtle one. The false light cause of action focuses upon indignity and defamation focuses upon reputation.

Question: How does the First Amendment to the Constitution affect defamation?

Answer: The free speech guarantees under the Constitution protect certain speech and commentary. The degree of protection generally depends on whether the person commented about is a private or public figure and whether the statement is regarding a private or public matter. According to the New York Times rule (from the case New York Times v. Sullivan), when the plaintiff is a public figure and the matter is one of public concern, the plaintiff must prove "malice" or "reckless disregard" on the part of the defendant. If both parties are private individuals, there is less protection for the speech because the plaintiff only needs to prove negligence.

Question: What is disparagement?

Answer: As defined in Black's Law Dictionary (7th ed. 1999), disparagement is "A false and injurious statement that discredits or detracts from the reputation of another's property, product, or business. To recover in tort for disparagement, the plaintiff must prove that the statement caused a third party to take some action resulting in specific pecuniary loss to the plaintiff."