In Gmail, BCC stands for Blind Carbon Copy. It is a way of sending copies of an email to other people without revealing who the email was sent to. When you use BCC, the recipients specified in this field do not appear in the received message header, and the recipients in the To or CC fields will not know that a copy was sent to these addresses. BCC is useful when you want to send an email to multiple people without each recipient knowing the email details of the others. It is also a great way to keep everyones email private when sending emails on a big mailing list. To use BCC in Gmail, you can click the "Recipients" field at the top of the email box, and then click "Bcc" on the right side. Then, enter the email addresses you want to BCC to and click "Send" to send the email to all.