The configuration editor allows a user to edit the configurations for RetroPie and Retroarch from a gui interface. Many common settings are set up so that a user can change the settings with a gamepad.
Manual configurations can also be set with the use of a keyboard.
The Configuration Editor can be accessed from the RetroPie Menu or through the RetroPie Setup Script and navigate to Setup ▶ Configuration / tools ▶ configedit
When changing settings, there are notes at the bottom of the screen that explain each setting and what they do.
When making manual edits you'll press
tab on the keyboard to exit out of the edit session. Whatever edits you have made will be saved when you exit the dialog gui.