Programs in the terminal behave consistently despite no standards. They follow certain rules, such as noninteractive programs quitting when pressing Ctrl-C, TUIs quitting when pressing 'q', and REPLs quitting when pressing Ctrl-D on an empty line. Most programs support readline keybindings, disable colors when writing to a pipe, and use '-' to mean stdin/stdout. These rules are descriptive, not prescriptive, and understanding them helps in using terminal programs effectively.