This is the 390th most frequent Italian word.
possano
"Possano" is the third-person plural present subjunctive of "potere," meaning "they may" or "they might."
Here, 'possano' is a verb in the present subjunctive mood used to express a possibility or wish after 'spero che' (I hope that).
Spero che possano venire alla festa.
I hope they can come to the party.
'Possano' is in the subjunctive mood, indicating necessity or importance after 'è importante che' (it's important that).
È importante che possano partecipare alla riunione.
It's important that they can participate in the meeting.
In this sentence, 'possano' underlines uncertainty and conditional capability after 'non sono sicuro che' (I'm not sure that).