What is the meaning of "لَّا شَرْقِيَّةٍ وَلَا غَرْبِيَّةٍ" in surah Noor verse 35?

What is the meaning of "لَّا شَرْقِيَّةٍ وَلَا غَرْبِيَّةٍ" (neither Eastern nor Western) in surah Noor:35 ? > God is the Light of Heaven and Earth! His light may be compared to a > niche in which there is a lamp; the lamp is in a glass; the glass is > just as if it were a glittering star kindled from a blessed olive > tree,] which is [neither Eastern nor Western, whose oil will almost > glow though fire has never touched it. Light upon light, God guides > anyone He wishes to His light. God composes parables for mankind; God > is Aware of everything!