1) An issue of fact, not law. A question of fact is resolved by a trier of fact, i.e. a jury or, at a bench trial, a judge, weighing the strength of evidence and credibility of witnesses. Conversely, a question of law is always resolved by a judge.
2) In some jurisdictions, an issue regarding the determination and/or interpretation of foreign law in a case. A party seeking to rely on foreign law must prove it like any other fact that has not been judicially noticed. In some jurisdictions, a question of fact regarding the determination and/or interpretation of foreign law is resolved by a jury or, at a bench trial, a judge.
See, e.g. Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996) (regarding questions of fact generally) and Griffin v. Mark Travel Corp., 724 N.W.2d 900 (Wis. Ct. App. 2006) (regarding foreign law).