Prepositions are invariable words which link two clauses of a sentence. An example of a preposition in English is the word with. For example, I go with Maria. Italian, just like English, has prepositions. Following is a list of prepositions in Italian and their various meanings.
di → of, from, than a → to, at, in da → from in → in, at, to con → with su → on, up, over per → for tra (fra) → between, through
As you can see, most of these prepositions have a variety of English equivalents. An exact translation depends on context.
Some prepositions combine with definite articles, forming a single word. These combinations are known as preposizioni articolate. These can be either the visual sum of the two components (a + gli = agli) or they can undergo slight changes due to phonetic phenomena of various nature (di + il = del, in + la = nella). In the following table you can see which prepositions combine with articles and how they do so.