Usually the Italian preposition in means "in" in English, but it can also mean "to" or "by"! The preposition in is used in the following cases.

1. To express the idea of going somewhere or staying somewhere (with countries, continents, regions, large islands, and addresses):

Vado in Italia. (I am going to Italy.)
Vado nella Sicilia. (I am going to Sicily.)
Abita in Germania. (He/she lives in Germany.)
Roma è in Italia. (Rome is in Italy.)

2. In describing a method of transportation:

Andiamo in macchina. (We are going by car.)
Andiamo in autobus. (We are going by bus.)
Viaggiamo in aereo. (We are traveling by plane.)
Viaggiamo in barca. (We are traveling by boat.)

3. In dates—note that nel is the contraction for the prepositional article in + il:

Cristoforo Colombo è nato nel 1451. (Christopher Columbus was born in 1451.)
Caravaggio è morto nel 1570. (Caravaggio died in 1570.)