Today Pastor Mike asked me what cc and bcc were for in writing email. i kinda explained what i knew but i was curious what exactly those were meant. here is explanation from wikipedia.com

E-mail
The term Cc has found renewed use with the growth of the Internet. It's purpose is the similar even though its implementation has changed.
In e-mail, the abbreviation "Cc" refers to the practice of sending a message as a "carbon copy" or "courtesy copy". That is, the receiver is not expected to reply (although they may, of course). Typically, supervisory personnel are notified with Cc.
Contrary to popular belief, Cc is not meant for sending multiple copies, at least, not particularly. It is a perfectly legitimate practice to populate the To: field with several addresses.
The Cc recipients are revealed to all recipients, and this may not be desirable, depending on the situation. An alternative field, Bcc or blind carbon copy is available for hidden notification. In common usage, To field recipients are the primary audience of the message, Cc field recipients are others whom the author wishes to publicly inform of the message, and Bcc field recipients are those surreptitiously being informed of the communication.

Blind Carbon Copy
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In the context of e-mail, blind carbon copy, abbreviated BCC, refers to the practice of sending a message to multiple recipients in such a way that what they receive does not contain the complete list of recipients.

There are a number of reasons for using this feature:

• To send a copy of your correspondence to a third party (for example, a colleague) when you do not want to let the recipient know that you are doing this (or when you do not want the recipient to know the third party's e-mail address).
• When sending an e-mail to multiple recipients, you can hide their e-mail addresses from each other. This is a sensible anti-spam precaution because it avoids making a long list of e-mail addresses available to all the recipients (which is what happens if you put everyone's address in the To: or CC: fields). For this reason, it often makes sense to use the BCC: field for mailing lists. Some viruses also harvest e-mail addresses from users' cache folder or addressbook, and large CC lists may further the propagation of unwanted viruses, giving another reason to use BCC.

'BCC' is also occasionally used to make certain types of spam e-mail look more convincing—by hiding your e-mail, the spammer hopes to trick you into believing you've accidentally received an e-mail that was not intended for you.

Basically, any recipients can see all e-mail addresses specified in the To: and CC: fields. No recipients can see any e-mail address (other than their own) in the BCC: field. In short, To: field recipients are the audience of the message, where CC: field recipients are others whom the author wishes to publicly inform of the message and BCC: field recipients are those surreptitiously being informed of the communication.