What is the monaco editor
The monaco editor is the editor API that repl.it uses for the editor. Without the monaco editor repl.it probably would be using another editor but the monaco editor is really cool and I enjoyed working with it.
Does it run code
The monaco editor doesn't run code, it only allows you to create an editor. You have to create your own way to run code. Maybe a connection to a remote computer or something else.
What is the repl
The repl below is just an example of the monaco editor you can find more info on the official website.