Basically, in AGS, you can add a "thing" to a room (such as an item, a plant, a guard, a flowing waterfall) by declaring it as a character or an object. On first sight, characters and objects are pretty much what you'd expect them to be, but beneath the surface, the engine handles them in a different way. (a major difference is that characters can move between rooms and objects are stuck to the room they're placed in) If a guard never moves and never speaks, you could consider making him an object. If your game has a moon in the sky that appears in multiple rooms and must be scaled manually ever so often (only characters can be scaled manually), you can make it a character while you'd expect a moon to be an object instead.
And Fluxmaster, that seems to be somewhat similar to the anchoring thing I mentioned. For instance, a brigand's idle animation might be 30 pixels wide, but if his dodging-west animation moves him 30 pixels to the left, displaying those frames would make the brigand skip 30 pixels to the east, sidestep to the west, sidestep back to the east, then skip back 30 pixels to the west. So what we do is simply add 30 pixels to the left side of his idle frames and put the brigand object 30 pixels to the west to even things out. This is an easy way to avoid the skipping-issue and requires less calculating than if something is anchored center. We don't need to keep his dodging-east frames in mind, because those automatically adapt.
