BCC is an option in your email to allow you to hide email addresses.
BCC is an abbreviation for Blind Carbon Copy and the name comes from when typewriters were used. To get extra copies of letters that you wrote you would use carbon paper and put several sheets of paper in. Then as you type the striking of character hit ribbon and top page and impact hit carbon paper (paper basically cover in toner in today’s terms) which put the character on the next page. If you wanted receiver to know you made carbon copies you added at end CC and names. You could also do carbon copies and not note on the original where sent so they were blind carbon copies.
In the email word you have three different entries you can list recipients of the email. In the TO you usually list who it is written to. In CC you list others you are sending it to also, but everyone sees all the names and addresses of people listed in TO and CC.
The third line is the interesting one and is BCC. When you list people there, they get the email (and see what everyone else sees) but their names and email addresses do not appear in the email.
Two big reasons to use BCC
First if you are sending to a bunch of people (I like to define as more than five) then one name in TO and the rest on BCC there is not that long list of names and addresses at beginning of email the reader has to get through to get to the message. Your recipients like you.
Second. If spammers get a hold of an email with a list of names on it, they love it. If a recent email, then probably all the addresses are good. They can sell them and make money. Also, because it is a group of names related somehow, if they send a phishing email to that group, they can make look like from one of them and get a better response rate, more money. If you had used BCC all they see is the one name/address sent to and you as sender. All rest are protected, so little value. Even less valuable is put your address in TO and all they got was your address.
Emails do get forwarded and spammers get those all the time.
Use BCC and make your recipients like you better and less phishing emails for you and them.