B-theory, or the "block universe" theory, is a philosophical concept about the nature of time. It suggests that all points in time—past, present, and future—are equally real and exist simultaneously. In this view, time is not a flowing river but rather a landscape where every moment is fixed and unchanging. According to B-theory, events do not occur in a linear sequence; instead, they are like frames in a film, all existing at once. This contrasts with A-theory, which posits that only the present is real and that time flows from the past to the future. B-theory challenges our intuitive understanding of time and raises questions about time perception and change.