Support files can be generated by visiting the "Developer Tools" page in the Dashboard. Two support files will be generated. One, called "__IDE_SYMBOLS__.php" provides class mappings used to help your IDE find classes. This allows a class like \Area to be mapped to \Concrete\Core\Area\Area in your IDE.
The second file, called ".phpstorm.meta.php" is used by JetBrains PhpStorm or IntelliJ IDEA products. It contains a list of all services that could be returned by calling Core::make() allowing for PhpStorm to detect what type of object Core::make() will return.
IMPORTANT: For PhpStorm or IntelliJ IDEA to detect the file after initally creating it you must invalidate the cache in your IDE (File -> Invalidate Caches/Restart).
Both files are placed in the package's main folder. If you generated these files using the Grunt script from Concrete5's git repository you must delete them. They are located in the folder /concrete/src/Support with the names __IDE_SYMBOLS__.php and .phpstorm.meta.php.
You should update the support files anytime Concrete5 is updated by returning to the Developer Tools page and clicking the button so your IDE has the latest IDE symbols and metadata files.