Intrinsic and extrinsic semiconductors differ in their conduction mechanisms and origin of defects. Intrinsic semiconductors have conduction between the valence and conduction bands, while extrinsic semiconductors are doped with other elements to create acceptor or donor levels near the bands leading to p-type or n-type conductivity respectively between the bands and these defect levels. The document discusses the electronic structure and defects in intrinsic and extrinsic semiconductors.