Moving photos to cloud, where does the iPhoto library file sit?

Now that I’ve got a decent fibre connection, I want to move my photos to iCloud. Currently I keep my photos on an external drive, which are all bundled into the iPhoto library file. I’ve looked at several YouTubes on the subject, but I’m not clear about one thing … when transferring photos to iCloud does the iPhoto library file simply relocate to iCloud in the same way that I moved the iPhoto library from my internal MacBook Pro disc to the external disc. I want to do the same thing with iTunes and noticed that iTunes has a similar library file so I assume what goes for photos goes with iTunes right?