A little bit of plain English
⭐1) Federal Circuit = Federal appellate court with exclusive jurisdiction over patent law. (Only US Supreme Court can reverse them.) The losing party at the trial court, which are U.S. district courts around the country, have to appeal patent matters to the Fed. Cir.
⭐2) patent prosecution history = interaction between applicant (usually their patent lawyer) trying to get a patent and the examiner who has the authority to issue the patent at the USPTO. The applicant’s own words, in their responses, can be used against them later in litigation, as admissions of what their invention doesn’t cover. This is really in the court’s equitable powers (e.g., prosecution history estoppel).
⭐3) claims = look at the end of a patent for these; they describe the scope of legal protection (i.e., broad or narrow) for the patent. Shorter claims that use more words are typically broader (and cover more products/services); conversely, longer claims are typically narrower. Claims are considered synonymous with the invention itself. So, they’re super important.
⭐4) intrinsic evidence = this is a fancy way of saying what is essential to the patent itself. In a patent suit, to determine what the claims mean (claim construction), the Fed. Cir. puts huge emphasis on (1) the claims themselves; (2) the specification (which describes how the invention works); and (3) the prosecution history. On the other hand, very little weight is given to the “extrinsic evidence,” meaning things outside the patent, such as outside texts and expert witness testimony. (The latter are important later, after the claim construction.)
⭐5) claim construction (or Markman construction) = what the claims mean. In patent suits, defendants argue the claims are narrow (or narrow enough) that they don’t cover their product/service, and so there’s no infringement; plaintiffs (patent owners) argue the opposite, that their claims are broad (or broad enough) that they cover the defendant’s products/services, and so there is infringement. In Markman v. Westview, the Sup. Ct. held that claim construction is a question of law, determined by the court (the judge). On the other hand, whether there is infringement is a question of fact for the jury. Each side submits its claim construction brief, makes its oral arguments in a Markman hearing, and the judge issues a Markman order. Hugely important — over 90% of cases settle after the order, since each side will know how strong or weak their case will be going into trial.