Articulated prepositions are the contractions of certain Italian prepositions with definite articles. In English, contractions like "I’m" and "won’t" are optional and indicate informality. In Italian, however, preposizioni articolate are required, regardless of the register you’re speaking or writing in. 
In English, we use ‘s (apostrophe s) to indicate that one noun possesses another. The Italian equivalent is the preposition di, with the order of the nouns reversed. A2 - Low-Intermediate Italian • possession • word order
One of the eight Italian parts of speech, prepositions are short but essential words which are placed after a verb, noun, or adjective in order to indicate a relationship between that word and the noun or pronoun that follows. 