Are these the same as VHS tapes in the sense that you can record over parts you don't want while leaving stuff in the begining intact? Thanks.

DVD-RWs can be recorded on, and then erased. You can record multiple shows onto an RW one at a time. But with most dvd recorders, you will not be able to erase, say program 2 (out of 4 on the disc), and regain that space to record something new. Some recorders will simply 'cloak' the erased segment from the disc's directory-it's still there, but the instructions written to the disc tell the recorder or dvd player (after the disc is finalized ) to skip it during playback, and go on to the next.

To erase a RW disc, you will have to reinitialize it, and that will erase everything.

To do the "record over one show without erasing another" trick you need to use DVD-RAM discs. But not all recorders or players can handle DVD-RAM.

Not quite true. Most DVD recorders will let you erase on recording from a RW disc containing multiple recordings, and re-use the erased space without erasing the entire disc. However that practice comes with a warning that if your recording runs longer than the free space, the recorder will keep on recording and overwrite the following recording on the disc. Some recorders have a setting to enable or disable automatic re-use of erased free space.

Not quite true. Most DVD recorders will let you erase on recording from a RW disc containing multiple recordings, and re-use the erased space without erasing the entire disc.

Only if the recorder allows VR mode on RW discs, and many do not. Only VR mode allows editing. The structure/format of DVD-Video does not allow this. They can make a portion of the disc appear to be "erased", but the space is not regained.

For all the Panny owners including me, from what I've seen of my neighbor's Samsung in the "VR" mode with -RW discs they work exactly like a RAM disc does & you can erase any Title. Example:

RECORDED IN THE "VR" RECORDING FORMAT:
TITLE 1
TITLE 2
TITLE 3
TITLE 4
TITLE 5
TITLE 6

You can ERASE TITLE 2 & TITLE 5 if you wanted too & record in that space again. BUT ONLY IF THE DISC IS SET TO RECORD IN THE "VR" Recording Format not the "V" Recording Format.