Burn any Bootable CD from a file and you may come across something called an ISO it can also be known by other format types such as one or more of the following, this by know means is a definitive list.
* BIN/CUE
* BWT, BWI, BWS, BWA
* CCD
* CIF from Adaptec Easy CD Creator
* CSO (.cso)
* DAA (.daa)
* LCD from CDSpace
* MDF/MDS (.mdf)
* NRG (.nrg) (Nero Disk Image)
* DMG (Apple disk image) (.dmg)
* UIF (Universal Image Format) (.uif)
* IMA (.ima)
Getting commercial (encrypted) DVD's to play in Kubuntu, proved to be somewhat more of a problem than I first envisaged.
You can find any number of web sites that give you clear instructions on what you must do; the priority being to install libdvdcss2, (the value for libdvdcssN is subject to change please ensure you have a current library) which is the library that decodes commercial DVD's. Almost all distributions do not include this, as the legality is open to some speculation. The large film corporations want you to buy DVD's, but are reluctant to let you play them on a computer!