Potere
In the present indicative tense, potere means "to be able to" or "can." For example:
posso uscire? (May I go out?)
Posso suonare il trombone. I can (am able to) play the trombone.
In the present perfect tense, potere means "to be able to, to succeed":
Ho potuto spedire il pacco. (I was able to mail the package.)
Non sono potuti venire più presto. (They could not come earlier, but they tried.)
In the conditional tenses (condizionale presente and condizionale passato), this verb may be translated as "could," "would be able to," "could have," or "could have been able to":
Potrei arrivare alle tre. (I was able to arrive at three o'clock; I would be able to arrive at three o'clock.)
Avrei potuto farlo facilmente. (I could have done it easily; I would have been able to do it easily.)