Each lane can provide up to a maximum of 1GB/s, thus giving the 16 lane slot the maximum 16GB/s, slower devices are categorized by the number of lanes they use from 1 to 16. Speeds are categorized by lanes, each with its own transmit and receive lines. PCIe wasn’t intended to run at full speed for all devices since most devices don’t really need that much to operate properly.
PCIe has totally replaced another standard called AGP which was specifically intended for graphics cards. The most common use for PCIe nowadays is with graphics cards which benefits hugely from the huge bandwidth provided by the interface. The difference in speed is quite huge when comparing the standard PCI slot which runs at 133MB/s to a 16 slot PCIe that can send or receive up to 16GB/s. It also utilizes individual buses for each of the devices connected to it instead of a shared one like what PCI uses. PCIe uses a serial interface instead of the old parallel interface used by PCI. The latest version of PCI known as PCI express is a much improved version in terms of speed.
Devices like sound cards, modems, NIC, TV Tuners, and some video cards have at some point or another have used the PCI port. The Peripheral Component Interconnect or more commonly known as PCI is a standard for connecting a lot of devices inside your computer to extend its capabilities.
