The open rate is the percent of successfully delivered emails that were opened while the clickthrough rate is the percent of successfully delivered emails were a recipient clicked a link within the email.
Open rate and clickthrough rate are both important email marketing metrics to tracked and can be improved by following best practices.
To increase your open rate, try optimizing your subject lines and send times. And to increase your clickthrough rate, make sure the content of your email is well written and your offer and Call-To-Action (CTA) are strong.