Preservation of Error
Also known as: Preserving an Issue, Preserving the Record
Properly raising an objection or argument at trial so an appellate court is actually allowed to review it later.
An appellate court can generally only review issues that were properly raised and preserved in the trial court. If a trial lawyer never objects to something, or never puts an argument on the record, an appellate lawyer typically cannot raise it for the first time on appeal, no matter how strong the argument would have been. Preservation happens during trial, not after it.
This is the practical reason appellate counsel sometimes gets involved before judgment: watching for preservation issues while a case is still being tried, rather than discovering after a loss that the strongest argument was never preserved. FloridaOnAppeal.com's best-practices guide for trial attorneys covers exactly this.