Modern computers have evolved considerably from what they once were. This is apparent in many aspects, from processor and bus speed to hard drive capacity and video/graphics capabilities. However, one less obvious evolution (to many consumers, at least) is the way peripheral connections have changed over the years.
Once upon a time, most peripherals (including the plug/connection interface and motherboard connection) were made as cards. These were inserted into slots in the motherboard at the back of the computer’s case. The interface was accessible from the exterior of the case, and the card’s tabs plugged into the motherboard slot.
Today, cards are still used in some instances (aftermarket graphics cards, for example), but they are no longer that common. Most peripherals have moved to an embedded format. Embedded peripherals offers several advantages both to consumers and to manufacturers, including lower production cost, less need to open the case to remove/install new cards and better ease of use.
Wikipedia defines a computer peripheral as, “a device connected to a host computer, but not part of it. It expands the host’s capabilities but does not form part of the core computer architecture. It is often, but not always, partially or completely dependent on the host.”