Two different organizations developed a DVD format, one format called Minus, one format called Plus.
They are very similar but not exactly the same. MOST modern DVD devices can handle both, but not all, so you need to read the documentation that came with the DVD device you want to use.
And there are two different types of DVD, called R and RW.
With R you write to it but cannot then delete that data to write to it again (although you can add data till it is full).
With RW you can write data, then overwrite it (read/write).
So with the minus format you can get DVD-R and DVD-RW
With the plus format you can get DVD+R and DVD+RW.
If you are going to create DVDs you need to make sure that the device you are going to play them on can support it.
So if you are going to use your PC to create a DVD on a DVD writer, but play it on your domestic DVD player, you need to make sure your player can support the format you use.
I tend to use DVD- all the time, but that is because my devices support it.
I think overall DVD- is the best supported format.