Manual input devices are those peripheral accessories of a computer system that allow users to directly interact with that computer and its systems. These range from video capture devices and cameras to a simple mouse and keyboard.
Many different input devices exist of varying degrees of complexity and the specific kind of data they are designed to enter into a computer. This raw data is processed by the computer and is put back out as coherent content that the user can comprehend. Every computer must have at least one manual input device, or their computer becomes little more than a television that can't be changed or interacted with. The means by which users are able to input data is ever changing, though, and when the only option was once a keyboard, today there are a wealth of different devices, some of which are able to read impulses from the brain and translate them into data that can be utilized by a computer's processor to control functions within its systems. There's little doubt that this technology will continue to evolve as the needs of users and the capability of developers change and improve over time. What the future may hold is anyone's guess.