Questions & Answers about Io sorrido e annuisco, perché capisco.
That’s right: Italian often omits subject pronouns because the verb ending already shows who is doing the action.
So this sentence could also be:
Sorrido e annuisco, perché capisco.
Including io can add:
- emphasis: I smile and nod
- contrast: maybe I understand, even if someone else doesn’t
- clarity in context
So io is not required here, but it is perfectly correct.
All the verbs are in the present indicative:
- sorrido = I smile
- annuisco = I nod
- capisco = I understand
Italian uses the present tense very often, just like English. Depending on context, it can sometimes also match English am smiling / am nodding / am understanding, although English usually prefers I understand rather than I am understanding.