Please explain the difference between the 'passato prossimo' and 'l'imperfetto':

The "passato prossimo" refers to events that are completed, but have some relation to the present.  Events which happened long ago can still be expressed in this tense when the event is seen as still having an active relationship to the present. For example: Io ho mangiato. I ate (have eaten). Avete capito quello che ho detto? Did you understand what I said? “L’imperfetto” is used to describe actions that are fully in the past, and are now over. These will have begun at some unstated time, and continued for an unspecified period. It expresses continuous or repeated past actions or events. It is also used to describe past weather conditions, time, or a person's age. Apart from the irregular endings, the verbs tend to drop the ‘re’ and pick up one of the following suffixes: -vo, -vi, -va, -vamo, -vate, and -vano. For example: Noi abitavamo a Firenze. We used to live in Florence. Io leggevo mentre lui scriveva. I was reading while he was writing.