Doping is the deliberate addition of desirable impurities to an intrinsic semicounductor to modify its conducting propertires.
The impurity atoms added are called dopants and the semi conductor so formed is called extrinsic semiconductor.
Depending on the type of impurities added, extrinsic semiconduictors are divided into two : n -type and p-type.
The extrememly pure form of semiconductor is called intrinsic semiconductor.
The conductivity of an intrinsic semiconductor is extremely low (but greater than insulators), and therefore as such there is no much practical use of intrinsic semiconductor. But when suitably doped to make extrinsic semiconductor, it works wonders. We get greater control over the flow of electrons.