Pacing in regards to writing is the rate at which big events happen. For example, a story would have slow pacing if it's mostly just people having small talk. When a murder or catharsis occurs, the pace picks up. When a piece of literature or filmography has bad pacing, the transition between slow and fast pacing is all but nonexistent. When it has good pacing, the big events are molded into the story appropriately and naturally. Hope this helped.
