I/O stands for input/output, which is any software or hardware device that can send and receive data to and from a computer
Input devices are those that provide input to a computer, such as a keyboard, mouse, microphone, scanner, etc.
Output devices are those that display or produce output from a computer, such as a monitor, printer, speaker, etc.
Some devices can do both input and output, such as a hard drive, network card, touch screen, etc. These are called I/O devices
I/O devices are important for communication between humans and computers, as well as between different computers or systems. I hope this helps you understand the meaning and types of I/O devices.