Avaialable light, is a term usually applied to intimate indoor and/or artificially lit subjects. Normally you have to open up the aperture and extend the time of exposure. However digital cameras are pretty notorious for not doing well in low light, the long exposure usually introduces a lot of "noise" into the photos and strange colour casts.
Squall in available light
Some cameras (like my Olympus) do have preprogrammed settings, usually called a night scene mode, that try to get the best reults with extended exposure times. This mode normally turns on white balance filtering and noise reduction and adjust the cameras effective ASA rating, to give best sensitivity in low light.
Using this night scene mode, I've found I can get some very usual landscapes (and seacapes) by using this mode just after it turns dark. The resulting photos usually have very rich, but slighty artificial colours.
The above image was actually taken in the dark with only just a slight after glow in the sky, but it looks like an errie twilight. The other amazing thing about this photo is how the lines of breakers have merged into a contious boiling mass of foam. That is because the waves were moving and must have covered the distance between each line of breakers within the 4 seconds of the exposure.