What is the difference between Cc and Bcc?

In e-mail terminology, Cc stands for "carbon copy" and Bcc stands for "Blind carbon copy". The difference between Cc and Bcc is that carbon copy (CC) recipients are visible to all other recipients whereas those who are BCCed are not visible to anyone. 

To specify the recipients, an e-mail message can contain addresses in any of the 3 following fields:

• To: field recipients are the audience of the message 

•  CC: field recipients are others whom the author wishes to publicly inform of the message (carbon copy) 

• BCC: field recipients are those being discreetly or surreptitiously informed of the communication and cannot be seen by any of the other addressees. 

It is common practice to use the BCC: field when addressing a very long list of recipients, or a list of recipients that should not (necessarily) know each other, e.g. in mailing lists.

Example of CC vs BCC

From: Frank Sinatra

 To: Kurt Cobain

Cc: Bob Dylan; Jim Morrison

Bcc: Mark Knopfler; Paul McCartney

In the above example, all recipients of the email (including Mark Knopfler and Paul McCartney) will see the following email header information when they receive the email:

From: Frank Sinatra

To: Kurt Cobain

Cc: Bob Dylan; Jim Morrison

This means that none of the recipients will know who the Bcc recipients are. Each of the BCCed recipients will, of course, realize that they were on BCC but they will not know who else was on BCC.