This report show how many ticket you receive per day, how many tickets you close per day. Or - per month. Or - per week. You can set the date range to report on and filter the report by category.
The second chart shows peak times during a week, the third chart shows distribution throughout the day. So you have the idea when to expect the most tickets (what day of week, which hours).
This report is very useful in understanding the dynamics of your customer support team. Does the number of tickets increase over time (and do you have to hire more people for the helpdesk team)? Are you closing less (or more) tickets compared to last year? Etc.