How is a key helpful in the identification and classification of an organism?

(N/A) key is a taxonomical aid used for the identification of plants and animals based on similarities and dissimilarities.
It is based on the set of contrasting characters generally in a pair,which is called a $couplet$.
This represents the choice made between two opposite options,resulting in the acceptance of one and the rejection of the other.
Each statement in the key is called a $lead$.
Separate taxonomic keys are required for each taxonomic category,such as $family$,$genus$,and $species$,for identification purposes.
Keys are generally analytical in nature.