The mappings in a package are divided into two classes, external and internal. The symbols targeted by these different mappings are called external symbols and internal symbols of the package .
External symbols are part of the package's public interface to other packages .
Symbols become external symbols of a given package if they have been exported from that package . A symbol has the same name no matter what package it is present in, but it might be an external symbol of some packages and an internal symbol of others.