Could someone please explain IFO and ISO.

[Articaine]

Im trying to understand IFO and ISO, differences, advantages, or disadvantages. I don't know much about them, all I know is that I backup w/dvdshrink, then make an image to burn with Imgtool. I downloaded DVD decryptor and it deals with IFO, ISO R and W.
Any help would be greatly appreciated.

Thank you