Explanation
A send log is a data extension that captures information about each email send, such as subscriber key, email name, subject line, and send time. It can also capture custom fields that are populated at send time, such as email address or personalized content. A send log can be used to analyze which email addresses receive which emails and when. References:https://help.salesforce.com/articleView?id=sf.mc_es_send_logging.htm&type=5