In the World Wide Web bounce refers to something that has come back. More specifically something that wasn't expected to come back. Colloquially we say that our mail has "bounced." This means that the e-mail that was dispatched from our mail box did not reach the intended recipients' mail box and the mail has come back.
Depending on the email provider you will receive the entire contents of your email or a truncated version. You may or may not receive any attachments that you sent along with the e-mail. There can be many reasons for an e-mail to bounce. The most common ones being that the intended recipient's mailbox was full or you typed in the wrong address. If you have typed in the wrong address then the address needs to be invalid for the e-mail to bounce, otherwise it will go to an unintended recipient. Sometimes the mail will bounce if there are issues with the server.
Depending on the email provider you will receive the entire contents of your email or a truncated version. You may or may not receive any attachments that you sent along with the e-mail. There can be many reasons for an e-mail to bounce. The most common ones being that the intended recipient's mailbox was full or you typed in the wrong address. If you have typed in the wrong address then the address needs to be invalid for the e-mail to bounce, otherwise it will go to an unintended recipient. Sometimes the mail will bounce if there are issues with the server.