Security codes are used as an additional verification step when you log in to the Client Portal, confirm withdrawals, or perform other operations. 

Security identities determine how you get security codes. You can check the current status of identities in the menu in the upper right corner and select Security & Access -> Authentication tab.

Security identity	How to get security codes
Google Authenticator	Codes are generated in the Google Authenticator mobile app.
Email	Codes are sent to your email.