Pro/Inralink is a database management utility from PTC, similar to Pro/PDM (also a database manager). It's intended purpose is to manage files and have a secure database. It is usually used by bigger companies that have to have a system to allow you to distinguish between R & D and Product files. If you have more detailed questions, email me.
Pro-Intralink is an attribute of Pro-E which helps in large scale data management for big establishments. It allows simultaneous working on large jobs and data sharing too. It increases the versatality and utility of Pro-E to a large extent.
Pro/INTRALINK is in simple terms a file management tool that uses a database engine to control Pro/ENGINEER or other document files. It features a secure file vault (called the CommonSpace) and a user work area (called the WorkSpace).
Product Items (or files) are checked out from the CommonSpace to the users WorkSpace. There the user can view, print, or edit (depending on permissions) the file. Any edited files are then checked in to the CommonSpace, which creates a new Product Item Version (a new file).
Since it is database driven there are reports available, plus a search tool for locating Product Items. Pro/E parameters can be linked to Pro/I, called designated parameters.
For security Pro/I uses Status Signals to inform other users what is happening with any file stored in the CommonSpace.
Pro/I also includes basic workflow processes, they they are very basic (which is why PTC has WindChill, a full featured PDM).
The other two replies state that Pro/I is for large install bases of Pro/E. Far from the truth. Any company that might ever use concurrent engineering on the same product needs Pro/I to control versions of parts, subassemblies and drawings. Pro/I configured and used correctly makes concurrent engineering 'almost' fool proof.
We have been using it for over 3 years, and it has saved us from resolving one year worth of potential problems if we had not been using it. Not the Pro/I does not have its own quirks.
Well excuse me Michael Jordan. Obviously you have more time to write essay's than I do. I make better use of my concurrent engineering time doing engineering, instead of trying to out-do someone's answer. If you would have read my response more thouroughly, I told him to email me if he had more questions.