Discovery is the process in every civil lawsuit by which the parties can obtain relevant information from each other to help in their claims and defenses.
The procedure differs a little in federal vs. state court, but the fundamental principles are the same. All parties have an obligation to provide information that is relevant to the lawsuit and reasonably requested by the other side.
It is important to know two things: (i) the discovery obligations apply whether the information is helpful to your case or not; and (ii) you have a duty not to destroy or discard relevant evidence once you know litigation is likely.
This can be hard for some people to get their head around, but remember these rules apply to the other side, as well.
There are three basic kinds of discovery:
Written discovery: these are written questions that must be answered in writing, as well as requests for production of relevant documents. Your attorney will advise you on whether any of the requests are outside the scope of the dispute or otherwise objectionable.
Depositions: witnesses with knowledge will need to give deposition testimony during discovery. This is sworn testimony, but not in court. Traditionally it took place in one of the lawyers' offices. Currently, some attorneys are choosing to continue using the videoconferencing technology that we used during the pandemic.
Expert discovery: if there is a need for expert testimony in a case (and often there is not) there will usually be a separate period of time for the parties to request and review discovery relevant to the other sides' expert's testimony.