As far as + and -, that applies only to DVDs (digital versatile discs). When DVDs first came out, the only recordable format was DVD-R. It was created by a consortium of manufacturers who owned the rights to manufacture blank discs and the drives that record on the blank discs.
As manufacturers raced to create a re-recordable format, manufacturers who weren't part of the consortium were heading down a different path toward a competing standard. Thus, standards emerged: the original - (or minus) version and a new one, + (or plus). So now there are DVD-R, DVD-RW, DVD+R and DVD+RW.
If you're creating video DVDs for playback in a DVD player hooked to a television, use DVD-R. They will play back (if properly recorded) in just about any player. In the years that I've been creating DVDs, I've run into several problems with people not being able to play back DVD+R media. To be on the safe side, however, I have a drive that can play back or record DVD-R, DVD-RW, DVD+R and DVD+RW.
Obviously, the RW on CDs stands for rewriteable just as with DVDs. The same warning about archiving is valid.
CF Card Differences
Q) How can I tell the difference between a Type I and Type II CompactFlash card? Also, what's the difference between a Microdrive and a CompactFlash card? Both appear to be identical except for the label.
A) The only difference between a CompactFlash Type I card and a Type II card is the thickness. A CF Type I is 3.5mm thick and Type II is 5mm thick. Devices are typically specified as being capable of accepting either just a CF Type I, or Type I and II, which makes sense since a thinner card will fit into a large opening, but a larger card won't fit into a smaller opening. A Microdrive is a miniature hard drive, whereas a CompactFlash is solid-state memory and has no moving parts.