Visits: the number of page views. Counted repeatedly.
Visitors: the number of users. Not counted repeatedly.
According to Cloudbric, a visitor is counted when someone visits your site. When one user visits your website 10 times in a day (from 00:00 to 23:59), it is counted as 10 visit. If someone visits your website once today and visits the next day, then it is 2 visits.
If for example, 1 person attempts attacks 10 times, it is counted as 1 visitor, 10 visits, 10 attacks, 1 hacker.