The key, as mentionned in the Analysis, is one of the two elements combined to form a Kanji (with exception of the keys themselves which stand alone).
The key is the classifier depicting tje material a Kanji is made of (wood, liquid, metal, textile…) or the "concept" it represents (human being, hand, feeling, speech…). Cf. example of the Key of the fish.
These caracteristics fine-tune the general meaning given by the basic phonetic primitive. Cf. example of phonetic primitive KEN.
The following list shows the most important keys. One can see that, by their generality, they allow to tidy up under their banner numerous Kanji ; they are entiteld to be called "large family". (For more detail about the weight of these 24 keys, see the diagram Keys-Frequency of occurence).
On the hill
On the software or appli, the screen displays the exhaustive list of other Kanji in common use classified under this key.
Cliking or pressing on their icons display their explanations and, therefore, allows to judge the scope and value of the classifier. Cf. the example of SAKU.