Computer accessories include all the pieces attached to the computers. Memory was expensive. Most early computers were sold in a least-cost format with options to buy more memory or a monitor or keyboard. Did you know the IBM Electric typewriter was modified to be used as the keyboard for very early computers? A teletype machine was also sometimes used as a keyboard for entry and a display, since the display was normally an answer to the computation.
This mode of selling accessories separately also allowed fast upgrades as the technology improved monthly. Upgrading from a cassette storage to a hard drive involved plugging into the back plane and changing the programming to see the new device. In the 1980’s it was common for the geeks to custom build or order a computer with the latest options sourced from different companies to get the power and flexibility they could afford. But as home computers became more popular, the all-in-one models also became very popular.