Lets first see what is SSRS
SQL Server Reporting Services (SSRS) is a server-based report generation software system from Microsoft. It is part of suite of Microsoft SQL Server services, including SSAS (SQL Server Analysis Services) and SSIS (SQL Server Integration Services).
Now lets see what is Caching in SSRS
"Caching is a mechanism to process the request and keep the response stored somewhere so that if the next time the same request comes, the response can be served the from the saved instance than generating the response again. Cache gets expired after defined schedule or occurrences of some events."
SSRS lets you enable caching for the report, in which case SSRS will maintain (store in ReportServerTempDB database) a copy of the processed report (along with data) in intermediate format so that if the same report request comes again, the stored copy can be rendered in the desired format and served.
In second part I believe you want to know the types of reports
You can create the following types of reports With Reporting Services -
1. Parameterized reports: a parameterized report uses input values to complete report or data processing.
2. Linked reports: a linked report is a report server item that provides an access point to an existing report.
3. Snapshot reports: a report snapshot is a report that contains layout information and query results that were retrieved at a specific point in time.
4. Cached reports: a cached report is a saved copy of a processed report.
5. Ad hoc reports: these reports can be created from an existing report model by using Report Builder.
6. Clickthrough reports: a clickthrough report is a report that displays related data from a report model when you click the interactive data contained within your model-based report.
7. Drilldown reports: Drilldown reports initially hide complexity and enable the user to toggle conditionally hidden report items to control how much detail data they want to see.
8. Drillthrough reports: Drillthrough reports are standard reports that are accessed through a hyperlink on a text box in the original report.
9. Subreports: a subreport is a report that displays another report inside the body of a main report. Conceptually, a subreport is similar to a frame in a Web page.
Credit : http://msdn.microsoft.com/en-us/library/bb630404.aspx