| Internal documentation is written in a program as comments. |
External documentation is written in a place where people who need to use the software can read about how to use the software. |
| Internal documentation would be comments and remarks made by the programmer in the form of line comments |
External documentation would be things like flow charts, UML diagrams, requirements documents, design documents etc. |
| Design documents, code comments, API documentation, test plans, user stories |
User manuals, help files, installation guides, release notes |
| Usually stored in internal wikis, repositories, and code documentation tools |
Can be in printed or digital format, and may include videos or interactive tutorials |
