Could someone explain the difference between PCI and PCI-E?

PCIe x16 Slots slot pci e Slot power · x1 cards are limited to A at +12 V and 10 W combined · x4 and wider cards are limited to A at +12 V and 25 W combined · A full- slot fire blaze When attached to a motherboard's PCIe x16 slot, a card such as the GeForce RTX 4080 can draw up to 75W from the + and +12V rails

slot machines game online So, there is no singular PCI Express slot There are actually four sizes : PCI Express x1, PCI Express x4, PCI Express x8, and PCI Express x16