Since 2004, SSRS has been the server tool of choice for generating custom online or email tabular data reports. It supports on-demand reports as well as emailing them out, in PDF, Word, or Excel formats.
With the SQL Server 2016 update, SQL Server Reporting Services has really come into its own as a business reporting tool. The latest updates have added a huge variety of GUI functionality, and taken what was a simple tabular reporting tool into the future with a wide variety of built in report widgets for displaying extremely slick data visualizations alongside the already existing array of simple graphs.
SSRS also supports SharePoint and Power BI integrations, as well as mobile specific reports.
In short, SQL Server Reporting Services is the way you get flat data into the hands of your users from anywhere in the SQL BI Stack, be it from a pre-built Line of Business App, a dedicated reporting data warehouse, or an OLAP Data Analysis Cube.