Can someone please explain what this actually does.

I think this causes it to immediately/automatically display/run the 'room description' String/Script Attribute upon entering a room (aside from the priority ordering controls). So, for example, if you want stuff to happen which adjusts/alters the 'room description' then you don't want it to be displayed before this stuff happens, which means you got to turn off the 'automatically generate room description', and then you place the scripting to run/display it when you're ready to do so. Or, you just don't want the room description to be revealed right away, is another reason to manually script when/where you want it to occur.

okay, thanks. Too bad it couldn't read from a list of words and then actually generate a random description ;)

well... you can manually script this desired action in, either:

1. not using (un-checking) the 'automatically generate room desc' toggle and then do scripting for when/where to display the (adjusted for your desired action) description, or...
2. you edit the built-in code of that involves how quest generates room description automatically and adjust (script: add/remove/change) its code to do this desired action

Yes, but wouldn't it be nice if the option to have it pull from a list of words to generate the description was already in the code? Kinda like those word games where you had to give nouns, adjectives and so on, to fill in blanks. You'd set up a description with wild cards in places, then create a list of words to use for those wildcards. Then, every time the player walked in, the description would be/might be different.

well... someone generous could do that (make a library of the desired scripting and add in the GUI/Editor tab/control tags)... lol. The problem is that most people are too busy to help out everyone, aside from Pixie pumping out public libraries... lol. This is one thing that quest needs a lot more of: quest is very powerful, but very little libraries have been done for it, for the public to use.

(this is just if you don't know where to find the documentation on the GUI/Editor tab/control tags, if you're interested in taking a look at them for whatever interest you might have with using them. I could probably create the above, but I am too lazy/busy to do so, and I'm sure it's the same for you, the too busy part lol, and everyone else too)

http://docs.textadventures.co.uk/quest/guides/using_types_and_tabs__advanced_.html (see the bottom half of this link/page, as the top half is just on using Object Types / Types -- quest's user level 'groups/classes')
http://docs.textadventures.co.uk/quest/guides/more_on_tabs__advanced_.html (this entire link/page is on the GUI/Editor tab/control tags)

this stuff was apart of Pixie's 'spell' library (a long time ago), but he/she probably has combined it into his/her 'combat' libraries, you can still see a small part of the spell stuff, here:

http://docs.textadventures.co.uk/quest/guides/simple_combat_system__advanced_.html

(I've not looked at Pixie's more recent combat' libraries of: 'combat v1.0' and his/her newest 'combat v2.0', so I don't know how much of the spell stuff was put into them, I'm guessing that it was entirely combined/put-in, but I've not looked at them yet myself)

I think most of these guides on the doc site are Pixie's too, at least it seems like its his/her writing to me, so my apologies to whoever if they're written by you and not Pixie.