Why do we need to inherit Exporter in our current package?

This is so the module can inherit Exporter's import method.

By writing the 2 lines above does the symbols present in the current package will be automagically exported to the program where we use this package? If so how?

To automagically export symbols Exporter uses the package variables @EXPORT, @EXPORT_OK and %EXPORT_TAGS from the class that inherits from it and exports as appropriate.