A deposition is a formal Q&A session where a witness (party or non-party) gives sworn testimony in response to questions from attorneys. There's no judge present; the testimony is recorded by a court reporter and often by video.
Depositions happen during the discovery phase of a lawsuit, before trial. The transcript can be used at trial for impeachment (catching a witness in an inconsistency), to refresh recollection, or in some cases as direct evidence if the witness is unavailable.
Skyline Legal prepares clients carefully before any deposition. Most depositions in PI cases last 2-4 hours. The most important rules: tell the truth, listen to the question, answer only what's asked, and don't volunteer.