What is the difference between scripted AI and Non-Scripted AI?

[darkely]

In Penumbra (the second game) when you walk into a small hallway (where you encounter the first monster if that helps you understand the area I mean) a monster comes after you (once it sees you) but if you run out the door (which triggers a load screen) the monster resets back to the end of the hallway.

So isn't the monster just scripted (or whatever you want to say) to walk up and down the hallway in search mode until it sees the player again? or what?