Good information in the repl tag right here on Stack Overflow:
About read-eval-print-loop
A Read-Eval-Print Loop (REPL) is an interactive interpreter to a programming language. It originated with LISP systems, but many other languages (Python, Ruby, Haskell, Tcl, etc.) use REPL’s to manage interactive sessions. They allow for simple experimentation with a language by bypassing the compile stage of the “code -> compile -> execute” cycle.
There are 4 components to a REPL (named in LISP notation):
- A read function, which reads input from the keyboard
- An eval function, which evaluates code passed to it
- A print function, which formats and displays results
- A loop function, which runs the three previous commands until termination