Learn more about how Lightning Deals work here
During Prime Day, some deals will run all day, but others will only be available for a limited amount of time, while supplies last. These Lightning Deals are usually open to everyone shopping on Amazon, but on Prime Day, they'll be exclusive to Prime members.
As their name suggests, Lightning Deals go quick, which is why you'll want to watch the deals you want (the app is the easiest way to do this). It is still possible to get a deal that has been 100% claimed if you add yourself to the deal's waitlist and another shopper bails on their purchase.