Hello Markbo. Arachne mentioned BD-R because you posted in the Blu Ray forum for hardware and media. A BD-R is a type of blank media burned by Blu Ray burners, and is not something you can use in your LG GSA-H42L, so not something you need to worry about.
+R and -R are two types of blank media that can be used in your burner. There are slight technical differences in them, but for most practical purposes you won't see much difference. I tend to burn +R disks myself, and if I wanted to burn rewritable disks, I'd definitely get +RW for that.
Your burner can also use Double layer blank dvds and it can write to DVDRam which is a type of rewritable disk. These are more specialized, and most people don't use them as they are more expensive.
Top burning speed for your drive is 18x on DVD +R and -R. We generally recommend you slow down the burning speed on most media, down to 8x or 12x. You can slow down the burn in the software you are using. If you'd like a recommendation for a good burning program, try ImgBurn. www.imgburn.com It is free to download and use.
And I'll second Arachne's recommendaiton for Verbatim. It is generally a safe bet for blank media.