the first key to understanding the VC project/build system is understanding what we do with the source files in a project.
each file in a VC project (foo.cpp, for instance) has a "tool" associated with it, based initially on the file's extension. the default tool assigned to foo.cpp would be the c++ compiler tool. the tool can be changed by the user if they so desire, but usually the default tool is appropriate.
when a project is built a tool gets called to do its stuff. usually that means spawning a process to run a command-line executable that does the actual work. for the C++ compiler the command-line tool that gets spawned is cl.exe.
tools also have properties that can be set on them, which generally are transformed into switches on the command-line tool. for instance setting the "Treat warnings as errors" property on the C++ compiler tool causes the "/WX" switch to be sent to cl.exe.
the properties on a tool are visible in "Property pages" dialog. to open this dialog: right-click on the project node in the "Solution Explorer" window and select the "Properties" menu item. select the "C/C++ compiler" node and you will see the "Treat warnings as errors" property in the property grid.
i'll talk more about the property pages dialog and properties in my next entry.