Those nocturnal emissions that you discover on your boxer in the morning or in the middle of the night is referred to as nightfall. In simple words, nightfall or wet dreams refers to involuntary ejaculation when a man is asleep through the night in the early hours of morning. Nightfall is frustrating, especially because an adolescent (who deals with wet dreams mostly) does not really know what it is and finds it embarrassing to speak to a parent or even peer about the same.
Usually, the frequency of nightfall varies from one individual to another, though most men experience it only in their adolescent years. However, there are men who suffer from nightfall throughout their lives. So, the condition is fairly common among men and does not really require medical attention unless they keep reappearing for a really long time.