A more thorough explanation:

Feudarum consuetudines

Feudarum consuetudines refers to the customs and laws of feudalism. It was a compilation of feudal laws and customs made in 12th-century Milan and is considered an authoritative work in continental Europe.

One example of feudarum consuetudines is the practice of vassalage, where a lord grants land to a vassal in exchange for loyalty and military service. Another example is the concept of primogeniture, where the eldest son inherits the entire estate of his father.

These examples illustrate how feudarum consuetudines governed the relationships between lords and vassals, as well as the inheritance of property within feudal society.