Kaal Sarp Yog and Kaal Sarp Dosh are one and the same thing. According to the prevalent definition of kaal sarp dosh, When in a Horoscope, all the seven planets namely Sun, Moon, Jupiter, Venus, Mars, Mercury and Saturn are placed between Rahu-Ketu Axis i.e North and South nodes of Moon, then Kaal Sarp Dosh or Kaal Sarp Yog is said to be formed in that horoscope. Depending upon the placement of Rahu and Ketu in the Horoscope, the kinds and effects of Kaal Sarp Dosh may differ and the persons having Kaal Sarp Dosh in their horoscope may suffer accordingly.
For example, a person may suffer from delayed marriage or disturbance in married life due to the presence of Kaal Sarp Dosh in his horoscope, whereas some other person may feel obstacles in his professional life due to the presence of Kaal Sarp Dosh in his horoscope, someone else may get some serious disease or diseases due to presence of Kaal Sarp Dosh in his horoscope and someone may not be having a child due to the presence of Kaal Sarp Dosh in his horoscope.
So the effect of Kaal Sarp Dosh will be different for every horoscope depending upon the placement of Rahu and Ketu and strength of this defect among some other factors in a horoscope.