In Italian, contracted prepositions are called preposizioni articolate. This means that the definite article and the preposition contract to form one word.
Attenzione! The prepositions per and tra (or fra) do not get contracted
Attenzione! The preposition con is usually not contracted, see the few exceptions below (col, coi, collo, coll’) and even those are often spelled out in written Italian: con il, con lo, con i, ecc.:
Examples of preposizioni articolate:
Il libro è sul tavolo. = The book is on the table.
Ci vediamo alla stazione. = We will see each other at the station.
Arrivano alle sette. = They are coming at seven.