It is the rate that shows how much of the e-mails that businesses send to their recipients and reach the recipients are opened.

For example, out of 100 e-mails you send, 95 of them are delivered to your target audience, but they may not be clicked and opened by the recipient. Clicks per open shows what percentage of those 95 e-mails was opened by the recipients. It is an important metric in measuring the success of e-mail marketing campaigns.