A DVD consist of two folders- a Video_TS folder and an Audio_TS folder- occasionally there might be additional folders, but those would contain extra elements, such as documents and other ROM contents.

To assemble the final DVD, all files are transcoded to mpeg2 (for video) and ac3 (for audio).

You cannot drag and drop files from a playable DVD into your editing software. You must rip the information from the Video_TS folder using a ripping program (eg. Cinematize) in order to convert the files into a file format that you can import into your editing system (eg. Quicktime).