PCI slots are rectangular, with a number of “pipes” that run down the length of the slot. Each pipe is typically wide enough to fit one card, but is also short enough that it doesn’t interfere with other cards.
The slots are located on the motherboard near the front, and are typically accessed by removing a cover – usually a small, triangular panel – on the front of the computer.
PCI slots come in different shapes and sizes. Some slots are long and skinny, while others are shorter and wider.
Some slots have multiple pipes running down the length of them, while others have just one. The number of PCI slots on a motherboard is typically proportional to its price.