Standart marketing campaign reports

Hi pros,

How should I read standart reports for e-mail campaigns?

Here is an example:

Somehow the ammount of sent emails from the campaign is less then the sum of delivered and non delivered emails on this picture. What are non delivered emails in this case? Also what are unique clicks in this context? And what are disallowed conact permissions?

Another repor I am not sure about is:

How are opened email rate, unique click rate and click to open rate are calculated?

Best regards,

Nadezhda Rukavishnikova