The speed at which it was recorded. The CD-ROM drive, audio player, DVD drive, etc. The recorder it was recorded on, and sometimes the recorder's firmware. A simple, safe option is to use whatever media is recommended for your recorder by its manufacturer. See your recorder's documentation, or check the manufacturer's Web site for this information.
Manufacturers often recommend their own brand of media, if they have one.
It's up to you to decide whether this extra cost is worth the comfort of knowing that the manufacturer has tested this brand and is satisfied that it works well with the recorder. Once you've found a brand that works well for you, it's easiest and safest to stick with it. However, be aware that discs which are identical in brand and type are not always produced in the same factories, and disc formulations can change slightly even from batch to batch, so your results may not be wholly consistent even if you always buy the same brand and type. The speed at which a disc is recorded can sometimes affect how easily it can be read or played. This is especially critical when writing at 4x speed to CD-RW media.