The peripheral component interconnect (PCI) slots on a motherboard are designed to allow direct interaction between secondary hardware and the central processor. Today, these components are attached directly to the motherboard, allowing the use of various internal components beyond the industry standards.
PCI technology was originally introduced in 1992 and eventually became a standard addition to all desktop motherboards. This allowed for the connection of advanced audio and video processors as well as other secondary hardware, such as network interface cards. While this same technology still exists in most PCs, it has been radically refined and streamlined in order to allow more efficient data transfer and more compact design. That said, most motherboards still have at least one standard PCI slot in addition to more modern versions of the same interface.
The benefit of a PCI connection is its high performance capability and dynamic configuration. This means that there are a myriad of different uses for a PCI connection, and virtually any device can be configured to use this port inside a computer in order to transfer and process information as well as send or receive data from the hard drive and central processor. Many hardware developers still rely on PCI connections for their products, hence its continued inclusion in nearly every desktop computer.