The first and most basic step of the refinement process is filtering out leaf stems, tips and dust from the aracha (unrefined leaf). The Japanese have a saying, mottainai ("it's a waste")...almost a cultural philosophy of avoiding waste.
So instead of discarding what is filtered from the main leaf, the stems are made into kukicha, leaf tips into mecha, and leaf dust (very small bits or even the hairs from the underside of the leaf) into konacha.
This set contains 50 grams of each tea type derived from a sencha base. More rare are teas derived from a gyokuro or kabusecha base as can be seen from the Nakamura-en Tea Shop.