The genitive of apposition

This is probably the simplest form of the genitive after the possessive. Two nouns are put next to each other (in apposition) and the second noun is in the genitive, qualifying the first one (adding more information about it).

It is good to learn the art of speaking
which in Latin would be:
bonum est artem dicendi discere.
Here dicendi gives you more information about artem.

A further example:

quantum ad festos dies ludorum celebrandos ... conceditur.
Cicero Pro Archia 13