If you are asking for the meaning of the word "external" it means outside or 'out of' depending on the use in a sentence.. for instance an external light is one that you would have outdoors. An...
When compiling the source-program A, any symbol which is not defined in A itself (but somewhere else is defined) is called external.
externals are the outside parts of a computer like parts you can see
external
External, meaning outside. Thus, Outside(External) Skeleton.