SS-1 SCUD is the NATO designation for what are actually a family of Soviet-designed ballistic missiles, starting with the Soviet designation R-11, but including the R-17 and R-300 9K72 Elbrus. Given the many variants worldwide, SCUD is the best-recognized name. Later variants, the SS-1C had longer range but less accuracy, but guidance improved in the SS-1D and SS-1E much more accurate guidance. Iraq's variants literally welded together several SCUDs for greater range but light payload and even less accuracy; essentially a propaganda weapon.
The Soviet R-11 was an adaptation of the World War II German V-2 rocket, the first operational ballistic missile, and did not feature much more advanced technology. The German missile was of minimal combat effectiveness due to its inaccuracy and small warhead of high explosive, but the Soviets assumed a nuclear warhead would make up for the inaccuracy. Perhaps the greatest practical advance is that the R-11 used storable liquid propellants, rather than the cryogenic liquid oxygen used by the V-2.
Missile analysts worldwide tend to differentiate between "SCUD class" and more advanced missiles; there is a significant technological gap between the SCUD type and more accurate missiles, even with the same limited range but solid propellant. China, North Korea, Iran, Iraq, and other countries have produced derivatives, and North Korea and China have exported to numerous other nations.