If you're a manager and you want to monitor the activity of your employees, there are a few different ways to do that:
View all of their activity
You can see a feed of all activity (notes, emails, leads, tasks, etc.) by going to the Activity Report page. Once on that page, click the "Filter by user" option (in the page menu on the left) and you'll see an option to filter the results to only show activity for a specific user. The information on this page is just meant to be a running list of everything that's happening, so it's not great for aggregate reporting, but you can use it to monitor everything an employee has been doing.
View their Pipeline reports
You can click on "Reports" in the navigation bar to see find reports for each of your pipelines. Just like with the Activity Report, you can filter this report to only show contacts assigned to a specific user.
View their calendar and to-do's
If you set up calendar sharing when you added the users to your account, you'll be able to see everything your employees have scheduled. Just go to your calendar and click the checkbox next to a user's name to show their calendar and to-do's.