We have now seen both the passato prossimo (present perfect or conversational past), as well as the imperfetto (imperfect past or descriptive past). These past tenses have specific uses, expressing different, nuanced past events. As such, they cannot be used interchangeably. Following is a list of rules governing their respective uses.

1. The passato prossimo is used to express an action which began and was subsequently completed at a definite time in the past. The action may have lasted a long time or a short time, and it may have taken place more than once, but the action has terminated in the present. The passato prossimo answers the question: What happened?
   
   

   L’altro giorno Matteo ha fatto visita a Giuseppe. The other day Matteo visited Giuseppe. Valentina ha ballato fino a mezzanotte. Valentina danced until midnight. Abbiamo visto tanti animali. We saw lots of animals.

   
   
2. The imperfetto is used to describe how people or things were in the past. It is also used to describe past actions that were once habitual. The imperfetto expresses past actions that were repeated over a period of time, with no reference to their completion. The imperfetto answers the questions: What was it like? What was happening?
   
   

   La domenica visitavi i nonni. On Sundays you would visit your grandparents. Gianluca era un bravo ingegnere. Gianluca was a good engineer. La vedevo spesso. I used to see her often.

   
   
3. There are some specific cases wherein the use of either the passato prossimo or the imperfetto can create a nuanced distinction.
   
   
   1. The imperfetto expresses an action that was once ongoing. It can be used with another instance of the imperfetto is to describe a simultaneous action that was also ongoing, or with the passato prossimo to express an action that also happened, but which was not ongoing.
      
      

      Riccardo mangiava mentre studiavo. Riccardo was eating while I was studying. Riccardo mangiava quando è arrivata sua madre. Riccardo was eating when his mother arrived. Cantavamo mentre gli altri ballavano. We were singing while the others were dancing. Cantavamo quando abbiamo sentito un rombo di tuono. We were singing when we heard a thunder clap.

      
      
   2. The imperfetto describes conditions and states of physical, emotional, or mental being in the past. The passato prossimo expresses the onset of a state of being at a defined time in the past.
      
      

      Quando era bambino, aveva paura dei cani. When he was little, he was afraid of dogs. Quando ho visto il cane, ho avuto paura. When I saw the dog, I got scared. Tiziana aveva fame. Tiziana was hungry. Tiziana ha avuto fame. Tiziana got hungry.

      
      
   3. Avere and essere are often used in the imperfetto. Other verbs which indicate emotions and mental states are also frequently used in the imperfetto. These verbs include, but are not limited to: amare, credere, desiderare, pensare, ricordare, sperare, etc.
      
      

      Erano innamorati e non pensavano a nulla. They were in love and they weren’t thinking about anything. Speravo di laurearmi entro la fine dell’anno. I was hoping to graduate by the end of the year. Non ricordavano più ciò che era avvenuto. They no longer remembered what had happened.

   4. There are certain verbs whose meanings change in the imperfetto and the passato prossimo. The two most common are sapere and conoscere.
      
      

      Conosceva mia madre quando era giovane. He knew my mother when she was young. Ho conosciuto un bel ragazzo. I met a handsome guy. Sapevo che non era giusto. I knew it wasn’t right. Ho saputo che hai fatto pace con Domenico. I found out that you made peace with Domenico.

      
      
   5. The modal verbs-dovere, potere, and volere- change their meanings in the imperfetto and the passato prossimo. In the imperfetto, these verbs indicate an uncertainty about whether or not the action was actually carried out, whereas in the passato prossimo it is clear that the action was completed.
      
      

      Dovevo completare il saggio. I was supposed to complete the essay. Ho dovuto completare il saggio. I had to complete the essay. Non poteva accompagnare sua sorella. He couldn’t accompany his sister. Non ha potuto accompagnare sua sorella. He wasn’t able to accompany his sister. Volevamo cenare con Alberto. We wanted to have dinner with Alberto. Abbiamo voluto cenare con Alberto. We insisted on having dinner with Alberto. Alberto non voleva cenare con noi. Alberto didn’t want to have dinner with us. Alberto non ha voluto cenare con noi. Alberto refused to have dinner with us.

      
      

Fare il/da Cicerone è un’espressione che si usa quando una persona fa la guida di un museo, di una città, o una zona d’interesse turistico, artistico, oppure storico. La frase si associa, quindi, al viaggio per conoscenza e istruzione. Si usa dire fai il/da Cicerone a colui che si atteggia ad esperto di tutto e che, in modo saccente, da sfoggio delle molte conoscenze sull’argomento di discussione.

Cicerone era conosciuto come un uomo molto loquace ed eloquente. In alcune lettere, Cicerone descrive la Grecia e le residenze dei grandi uomini, con molta efficacia e diligenza. Questi scritti divennero famosi tanto che nel 1855, lo storico Jacob Burckhardt, pubblicò “Il Cicerone, guida al godimento delle opere d'arte italiane”.

Fare il/da Cicerone è un’espressione che viene letteralmente tradotta come to be or act as Cicerone, che in inglese non ha nessun significato. Nella lingua inglese non esistono espressioni simili e una frase che spiega meglio il suo significato sarebbe: "to act as a guide to somebody", "to show someone around".

Esempio 1:

Grazie per la visita al museo e per tutte le informazioni che mi hai dato. Sei stato un perfetto Cicerone.
Thank you for the visit to the museum and for all the information that you gave me. You have been a perfect tour guide.

Esempio 2:

Se vieni a trovami, prometto ti farti da Cicerone e di mostrarti tutte le meraviglie della mia città.
If you come to visit me, I promise to show you around and show you all the wonders of my city.

Esempio 3:

Sei vuoi un tour storico, fammi sapere. Sarò felice di farti da Cicerone.
If you want a historic tour, let me know. I would be happy to show you around.