This is the 16th most frequent Portuguese word.
ser
"Ser" means "to be."
The verb 'é' is being used to describe a permanent or intrinsic characteristic (profession in this case) of the subject.
Ele é médico.
He is a doctor.
The verb 'será' is used to indicate when an event is scheduled to occur in the future.
A reunião será amanhã.
The meeting will be tomorrow.
The verb 'ser' is used in an infinitive form within a modal verb phrase to express a potential state.