dvd+/-rw

While checking out the dell site, i came across a laptop with a config which had a "12.7" SATA Trayload DVD+/-RW?" Now what is this? Will it run the normal cds and dvds???

Well, I've observed this around...there are a few writable DVDs with DVD+RW and some with DVD-RW...also I've seen few really rare ones with DVD+/-RW...I don't seem to find much of differences...how are they different from each other?