DVDs can be DVD-Video or DVD-Audio. In a DVD-Audio, the VIDEO_TS folder would be empty (though usually those discs contain a DVD-Video portion as well, so players not equipped to read the audio part can still play it). In a DVD-Video, the AUDIO_TS folder is empty.

In all honesty, for 99% of players, you DON'T need the AUDIO_TS folder. But, there are a select few DVD players that read the AUDIO_TS folder first, and if it's not there they choke.

There should be an option in Nero to make a DVD-Video somewhere, or Video DVD, or whatever. Use that, drop the two folders in, and you're set. Alternatively, you can make a data DVD, drop in the two folders, and you're also set.