What is the difference between Reply and Reply All?

• 'Reply' sends your response only to the person that sent you the mail. Therefore, anyone to whom the mail was also sent or Cc'd will not receive your reply.
• 'Reply To All' sends your response to everyone the mail was sent to or were Cc'd.

Note: Anyone Bcc'd in the original mail will not receive your response. However, be very careful here, if you were Bcc'd and you reply to all everyone will now know that you had been Bcc'd.

This information can be found on this website: https://adminit.ucdavis.edu/tech-tips/reply-replyall-forward#:~:text='Reply'%20sends%20your%20response%20only,to%20or%20were%20Cc'd.