IETM Explained in Simple Terms. Not clear yet, let me put it in another way. When we purchase a Car, we get a user Hard copy of the manual has some 1000 pages. Similarly, when OEM (Original Equipment Manufacturer) delivers some big vehicle or machinery or systems having a lot of subsystems, then along with the Physical components, OEMs also delivers hard copies of manuals. https://www.codeandpixels.net/blog/tag/interactive-electronic-technical-manual/