An expansion slot is one of the slots on a motherboard into which an expansion card can be inserted to expand the functionality of the computer, such as a video card, network card, or sound card.

The expansion card plugs directly into the expansion port, giving the motherboard direct access to the hardware. However, since all computers have a limited number of expansion slots, it is important to open up your computer and check what is available before purchasing one.

Some older systems require the use of a riser board to add additional expansion cards. However, modern computers not only have ample expansion slots, but also have features integrated directly into the motherboard, which reduces the need for as many expansion cards.

There have been several different types of expansion slots over the years, including PCI, AGP, AMR, CNR, ISA, EISA, and VESA, but the most popular one in use today is PCIe. While some newer computers still have PCI and AGP slots, PCIe has essentially replaced all of the older technologies.