CPF is a type of identification number. You may be asked for your CPF-number when booking a bus or flight ticket. It is needed if you’re staying in Brazil for a longer period and want to open a bank account to receive a Brazilian salary. If you are staying for a only one semester or a year as an exchange student your RNE-number or passport is sufficient. If you would need a CPF in order to book a ticket, a helpful Brazilian friend can maybe help you!]

Here is a link for all the steps to get a CPF: http://www.liveinbrazil.org/getting-cpf/