If we take a look at the conjugation of many Romance languages, we will see that their forms come from Latin. However there are some peculiarities.
If we just look at French and Spanish, we will see that, in the 2nd person singular, the verbs have a common "-s" ending (tu parles). However, Italian does not. Instead, it has an "-i" ending (tu lasci).
So, why do we have the "-i" ending instead of the "-s" ending then? Is it due to some phonetic changes? Could someone could give me an example of how the verbs in this form changed over time?