What is the report Area in SSRS?

Report Area in SSRS is default page as and when you are creating any of the report or adding new report to your report project. In this area, you have report body. Report Area dealt with page setup for whole report, header, footer of the report. You can manage the report variables, assembly, classes and parameters as well via report area. 

Report area properties also setup and manage the page setup for whole report. You can also write the codes to provide the custom functionality to your report.