SSRS stands for SQL Server Reporting Services, a widely used Microsoft Technology for developing dynamic reports.
The executables for SSRS are known as rdls, Report Definition Language which is a mark up language which resembles like a XML when you view it in code view.
(SSRS files will have the extention as .rdl that has to deployed in the Report servers for using the application)
In order to develop SSRS reports we need to have the SQL Server R2 installed in our machine, with the Visual Studio Report Development IDE supporting the SQL server version.
In order to make use of the deployed rdl files in the report servers, we have to make use of the ReportViewer control, through which the Report can communicate with the website.
The main advantage of SSRS is, we can use various data sources like SQL Server, Azure, Oracle to generate the reports.
The effeciency of the Reports depend on the Queries we design.
It is always an advantage for a SSRS beginer to handle the most of the functionality in the Queries instead depending on the development interface.
Also, databases will always have a edge over the development server. So when you dont have huge logical dependencies in the Report side, your report will render very soon.