What is the difference between public and private emails?

Public emails are ones which are easily acessable by anyone and do not need any security checks.

Private emails are confidential or related to one person, company or group and are not to be disclosed or accessible to others.

In general, all email should be written as if it will become public as some time in the future because he email system is one of the earliest parts of the internet and is not designed for information security..