PCI Express Slot
PCI Express slots are both shorter and longer than PCI and AGP. The x1 slot is a single-lane implementation, while the x16 slot combines 16 lanes for peripherals such as the display adapter.
PCI-Express Vs. AGP
This display adapter from NVIDIA was one of the first x16 PCI Express cards on the market. PCI Express, AGP and PCI cards all have different edge connectors to ensure that they fit into the appropriate slots. (Image courtesy of NVIDIA Corporation.)
Learn more about PCI Express