The computer only responds to keyboard if the CPU is looking at the keyboard to see if someone had pressed a key. If the CPU isn't looking, the person can hit the keyboard all they want and nothing will happen. It translates the data in the video memory into symbols on the monitor. It can thus draw letters and graphs on the screen. They usually have their own ports, though the mouse often uses the serial port to connect to the computer.
Networks are a high speed method of transferring data from one computer to another.
The data highways inside the computer through which the information moves from one spot to another. Address bus wires carry the address of where the data is coming from or where it is going to. This tells the various components in the computer whether they should receive data from or supply data onto the data bus wires. They also carry timing information to help synchronize the various parts of the computer so they are all doing the right thing at the right time. The instructions that tell the CPU what to do.