what is the difference between local/Web data reports (RDLC) and SSRS?
SSRS (SQL Server Reporting Services) is a part of some editions of Microsoft SQL Server (SQL Server Express with Advanced Services as well as the non-free versions). It allows you to process server-side reports (.rdl
files).
The ReportViewer control (formerly included in Visual Studio, now available as a nuget package) allows you to process client-side reports (.rdlc
files). It does not require SQL Server.
Since both components use the same reporting engine, RDLs and RDLCs use the same XML schema. Thus, most material you find online for SSRS also applies to RDLCs.
The following MSDN article outlines the difference between RDL and RDLC files: