[swatkat]

There are 5 types of DVD Discs.
1] DVD-R
2] DVD+R
3] DVD-RW
4] DVD+RW
5] DVD RAM

Here Discs of type 1 and 2, above are similar to CD Recordables. That is they are one time recordables. The + and - are two different standards.

And Discs of type 3 and 4, above, are similar to Rewritable CD. That is they can written-erased-written. Here, again + and - are two different standards.

And the last one, DVD RAM, is the DVD which you can use like a Hard Disk/Floppy Disk. That is you can write/delete/edit data, without the need of burning. this makes use of a special file system called UDF.

A Singel layered DVD can have upto 4.7 GB size. A Double layered, as the name says it will have double writing layers, can effectively have double of 4 GB, that is 8 GB size.

Almost all newer DVD Drives support all the formats, and "-" format is more popular and compatible. You can go for any good DVD Drive (Reader or Writer).

But, not all DVD WRITERS support Double Layered Burning, and DVD WRITERS which support them are costly. So you can go in for DVD WRITER which has only single layered burning support.

And, ALL DVD READERS can read the DOUBLE LAYERED DVDs.