From Teflpedia

Of (strong form /ɒv/, weak form /əv/, very weak form /ə/) is the second most common preposition in English (after to) and the fourth overall most common English word.

It is used in a large number of ways.[1]

Note that students with Romance language L1s often use of inappropriately due to L1 transfer. For example a French learner might say *"Bonbon is the dog of Martin", which is a word-for-word translation of French "Bonbon est le chien de Martin" whereas a better translation would be "Bonbon is Martin's dog".