Email may have supplanted hard copy letters as the main form of communication in the 21st century, but there still is the occasional need to type a letter. In either case, you may want to send a carbon copy, or cc, to another recipient. With an email, you may want to send a blind carbon copy, or bcc, to another individual.
Type cc: below your signature line on a hard copy letter. Follow the colon with the names of all additional recipients of the letter
Use the cc: field in an email to keep others "in the loop." For example, if you are working on a project and want to notify your supervisor that you've completed the first phase, type his name into the To: field and type in co-workers' email addresses in the cc: field. They also will receive a copy of the email and can stay abreast of the project's progress.
Use bcc: when you want a layer of privacy. For example, if you are sending an email to business clients and would rather your list of clients be kept private, send the email to yourself in the To: field and place all recipients' email addresses in the bcc: field.