END is used to terminate the program.
When the ARMbasic is used in a control application, the END would not normally be encountered. As most control applications would be a loop, as when a program ends it would require the user to restart or a reboot.
There is an implied END added to any program. When a program ENDs, the last state of variables, IOs and IO controls is maintained. If a program is then RUN again those states will probably be different than running the program by hitting RESET. RESET sets all variables to 0, and all IOs to inputs. When a program is restarted from RUN, the variables will be set to 0, but the last IO state will be maintained.