Daiginjo (大吟醸) is a premium sake and regarded by many as the pinnacle of the brewer’s art. It requires precise brewing methods and is made from rice polished to 50% and below. Daiginjo sakes are usually served chilled to bring out their nice light, complex flavours and aromas.
Junmai daiginjo (純米大吟醸) is simply daiginjo sake that also fits the “pure rice” (no brewer's alcohol added) definition. It is also brewed with very highly polished rice (to at least 50%) and even more precise and labour intensive methods. Generally light, complex and fragrant.