"Yi Ji" (1st Grade) means the level of original tea material separated according to the size from tiny bud, young leaf to rough leaf and stem. The highest level is "Gong Ting" (Tribute) of nearly main tiny buds and the next is "Te Ji" (Special) of main tiny buds with few young leaves and then this "Yi Ji" (1st Grade) till "Jiu Ji" (9th Grade) of quite high ratio of rough leaves and stems.
For easy understanding(if not, we need some long articles from specialists'), generally the higher the level is, the bitterness is more obvious. In contrary, the lower level has more sweetness. Taste of tea is quite complicated due to the tea essences included and the later processing technology, so we can't say the higher level the better quality or sometimes we even can't tell the difference between near levels. Please don't mind if you have contrary opinions, you should be correct.
Storage:
Guangzhou natural storage.
Well recommended for daily drinking.