This is a formal process that takes place before the actual trial in many patent cases. The purpose is to help speed the trial along by sorting out in advance some of the details over terminology. If you’ve ever read a patent you know that the language can be confusing and hard to follow. You don't want to waste time during the trial haggling over grammar, punctuation, and technical terminology so instead you work out those issues in advance. Both sides explain their interpretation of the patent language, and the judge decides which interpretation he believes is more accurate. That’s the interpretation that will be used in the actual trial.