What is the difference between a series ohmmeter and a shunt ohmmeter?

Basically, your series and shunt ohmmeters differ in circuit configuration. Your series ohmmeter is configured in a way that your "meter" (which has internal resistance) is connected in series to your "measured resistor" and we all know that those TWO resistances will ADD up causing some sort of inaccuracy. While on the other hand, your shunt ohmmeter is configured in a way wherein your "meter" is connected in PARALLEL to your "measured resistor" that will ease-up the inaccuracy but will only measure resistances ranging from 200 Ohms to 400 Ohms (typically and depending on your configuration).