When SQL Server 2000 was released, it contained a new reporting feature named Reporting Services. Since then, it has gained enormous popularity and its technology is currently used in Microsoft Dynamics and other applications. Dynamics NAV, AX, GP, and CRM all use reporting engines based upon Reporting Services technology.
It's important to know what you can do with it because Reporting Services has much more to offer than the built-in reporting tools so you can make an educated choice when you decide to use an external reporting tool and compare it with other third-party applications.
First of all, it's completely free; it comes with SQL Server. When you make the investment in SQL Server, you get the reporting service (and analysis services) as part of the package. The only investment needed is the time to develop reports.