From Forum Nokia Wiki

If you want your programs to be buildable from the command line, you must write project files in a Symbian specific format. The files are:

• A project definition file (MMP file) that describes a project to be built. This is an environment neutral file that can be used by the tools to produce make files for any of the supported target environments. It also defines resource files to be built.
• A component description file (bld.inf), which lists a group of related projects, and gives additional build instructions.