Simple Shell is a UNIX command line interpreter designed to execute basic commands entered by the user. It prompts the user to input a command and waits for a single-word command followed by pressing the Enter key. After execution, it displays the prompt again for further commands. The shell handles errors gracefully, notifying the user if an executable is not found and providing a new prompt. It also addresses the "end of file" condition (Ctrl+D). In later versions, it was enhanced to handle command lines with arguments, implement the PATH variable, and introduce built-in functionalities like "exit" and "env." The "exit" built-in allows the user to exit the shell with an optional status code, while "env" prints the current environment variables. These iterations demonstrate the evolution of the simple shell project, adding functionality and improving user experience over time.