HourStack reports are extremely flexible and powerful. This is where you can see the breakdown of every project, team, user, etc. by entry. You can also see how far off your estimation (allocation) was from the actual time spent.
I don't want my team members to see my data. Can I stop them from creating reports?
While you can't stop them from seeing only your data, you can prevent them from having access to reports by using the permissions matrix which is described in detail here.
How is the utilization chart calculated?
The utilization percentage is calculated by adding up all users (in the report) allocations for each day and then dividing that by the total number of hours that are available for each user to spend. This is set in each user's week settings.