I was wondering what the different is between DVD+R, DVD+RW, DVD+R DL, DVD+RW DL, DVD-R, DVD-RW, DVD-R DL, DVD-RW DL?

I would also like to know what recordible optical DVD format works with all older DVD players or older and what works with the newer ones, also the speeds.

What is more common among manufacturers for recordible optical DVD media now, single layer, or dual-layer?

What brand or brands of DVD recordible media will last the longest after being recorded, I am thinking Sony since they have a great reputation (at least with me). Do R's last longer than RW's?

I ask these questions because I have absolutley no clue about these DVD media types except for what I posted and I want to get in it. ANY help would be very appreciated. Thanks!