product backlogs items VS sprint backlog items

Hi evey one, i have discussed with my SM about pbi and spbi but i don't understand very well about if a product backlog item is bigger than a sprint backlog item, i said yes because during refining you can split a pbi into a lot of pbis and then you can use during sprint plannning,and then in sprint backlog i would like to know about your experience, what do you think???