In English we use prepositional phrases to describe nouns; in other words, they are like adjectives.
"The Driver of the Bus" The prepositional phrase tells you what is the object of the person's driving; in other words, "of the bus" tells you that "he or she drives the bus." Similarly, you could say "the leader of the Greeks" or "the teacher of the class." In all these instances, the prepositional phrase tells you what would be the direct object of a verb which is hidden in the noun: "he leads the Greeks" or "she teaches the class." In Latin, when the genitive case is used to indicate the object of a verbal noun, it has a special name: the objective genitive.
"The love of God." The prepositional phrase tells you (probably, but see the next example) who it is that is loving; in other words, this phrase may refer to the fact that "God loves us". Similarly, you could say "the speech of the President" or "the screaming of the babies." The prepositional phrase tells you what would be the subject of a verb which is hidden in the noun: "the President speaks ..." or "the babies scream." In Latin, when the genitive case is used to indicate the subject of a verbal action, it is called the subjective genitive.
"My love of God." Here we have two different way of expressing the "possessive" case and they are used to distinguish what in Latin we call the objective genitive and the subjective genitive. That is, "my love of God" refers to the fact that "I love God." When put this way you can see that "my love" is a "subjective" relationship (speaking grammatically), while "love of God" is an "objective" grammatical relationship. In English we typically use the possessive forms and adjectives to express the "subjective" grammatical relationship; and we use the prepositional phrase ("of") to indicate the "objective" grammatical relationship. Consider: "maternal love" = mothers love children; "divine care" = God cares for humans; "Roman aggression" = the Romans attack foreigners; "authorial presence" = the author is present; etc.
"Rivers of milk and honey." Since prepositional phrases in English can be used to turn nouns into adjectives, they may be used to indicate any number of relationships. In this case, we know from the content that milk and honey are the actual substance of the rivers; in Latin, such expressions are called "genitive of description or material." Consider: "a wall of brick" = "a brick wall"; in both cases "brick" is the material description of the wall.