Question about CD/DVD burning

Frequently when I burn CDs or DVDs, I see the option for "Disc-At-Once" and/or "Track-At-Once". It seems to be a fairly common feature as I see it in Nero, AShampoo Burning Studio, and other burning apps. What exactly do these things mean, and what difference can they make in burning something? I just burned a large ISO file to DVD and was given the option to use Disc-At-Once. I didn't check the box; does it matter? Sometimes "Track-At-Once" or "Disc-At-Once" is checked by default and I always just leave it as is, and it has never seemed to effect anything one way or the other....

 

(above quote is from a different thread)
Thanks, but there's also the option to "Finalize disc" or "Allow files to be added later" depending on which program I burn with. These options are in addition to the "Disc-At-Once" option. When burning ISO images and videos for the home DVD player, I always finalize the disc. I was mainly wondering why the options for "Disc-At-Once" and "Track-At-Once" are even there, and what difference they would make. I have burned dozens (if not hundreds) of discs and very, VERY rarely have any kind of issue with them not working on other PCs, and when I do, I can't remember one single instance where it was because of the disc. In the rare event that the disc doesn't read properly, it has always been either a Windows problem or a hardware/drive problem.
Anyway- This isn't really a big deal, I was more curious than anything....

Thanks
[dlb]
:major