A cold open (also called a teaser sequence) is a narrative technique used in television and films. It is the practice of jumping directly into a story at the beginning of the show before the title sequence or opening credits are shown. In North American television, this is often done on the theory that involving the audience in the plot as soon as possible will reduce the likelihood of their switching from a show during the opening commercial. A cold open may also be used to recap events in previous episodes or storylines that will be revisited during the current episode.
https://en.wikipedia.org/wiki/Cold_open