DVD-R/DVD+R ??? Sony DRU-120A

[dlmcminn]

Can anyone please answer what is the difference between -/+ on the DVDr disk? I have a Sony DRU-120A burner and it says it writes on DVD+R but it doesn't say its compatible with DVD-R. And my Panasonic DVD-CV37 dvd player playsDVD-R. I have Ripped and burned "Tme Machine" on to a DVD+R which only plays on my Computer. Can my burner also burn onto DVD-R? is there really a difference?.....Please help I dont want a bunch of Coasters......I have enough....thanks