Pampers Swaddlers are just diapers that are mostly meant for your baby to wear during the daytime when you'll be changing the baby more often.
But for Pampers Swaddlers overnights the Pampers Swaddlers overnights are a more absorbent version of the regular Pampers Swaddlers diapers which means that the Swaddlers Overnight diapers will hold up longer while the baby is asleep so the baby won't need to be woken up to change their diaper.
Some babies wet more through the night than other babies so your baby may need a more absorbent diaper to sleep through the night and prevent diaper leaks at night so if your baby is leaking through diapers at night then you may need to put your baby in overnight diapers.