What format do DVD players accept?

They vary depending on make and model. Some support the reading of many formats such as AVI, MPEG, Divi, DVD, VCD, MP3 and MOV.

Others are more fussy and only play DVD or CD. Check the specification before purchase. In my experience the cheap, unbranded ones, seem to be the most flexible.

If you mean what is the format on a DVD disk.

The files are arranged in large blocks of video with the extension *.VOB, VOB seems to be similar to an MPEG file.

Other files are there for menu systems and other features.