Subcategorization is a natural language phenomenon, which denotes the tendency of heads

Head (linguistics)

In linguistics, the head is the word that determines the syntactic type of the phrase of which it is a member, or analogously the stem that determines the semantic category of a compound of which it is a component. The other elements modify the head....

 to have restrictions on the arguments they can take. For example, some verbs do not take a noun-phrase complement, while some verbs do take a complement, or even two complements (in some theories), typically cast in traditional grammar as (direct and indirect objects). The name subcategorization comes from the fact that the category of a head can be divided into finer-grained subcategories of different types of each head based on the arguments they take.