What's the difference between DVD-R and DVD+R?

DVD-R and DVD+R

DVD-R was the first to be introduced and is still the most widely used format among professional users. (2006). DVD+R is widely sold in retail outlets and has become more popular among home users.
DVD+R was introduced in early 2002 as a competing format. ---- Proponents claimed better compatibility among readers, although tests show that compatibility is roughly equal.
Hybrid drives that can handle both formats, usually labeled "DVD±RW", are very popular since there is not a single standard for recordable DVDs. There are a number of significant technical differences between the dash (also sometimes called "minus") format and the plus format, though most consumers would not notice the difference.
Original companies in the “-R "camp:
Pioneer, Toshiba, Hitachi, Matsushita Electric (Panasonic).
Original companies in the “+R "camp: