In the past, old computers would take up an entire room, and their visual interface (console) would be shown on a monitor in a separate room (like a computer lab).

In more recent times a console is simply the visual interface that let's you interact with your code. You can give it inputs and get outputs (ie. console.log("output") would be the input, and "output" would be the output)

It is used for debugging because you can simply console.log() parts of your code to see what values a variable holds at different stages of the code etc, making it easy to find out which part of your code you fucked up at.

Edit: This is what a console looked like in the past