difference between CD-R 24X and CD-R 48X

[TK2014]

I was wondering for example, if you put a CD-RW 24X media into a CD burner, how does the drive know to write this media at 24X speed? Is there a difference in the structure between this 24X CD-RW and let's say 4X CD-RW media? Are the grooves in the media smaller?
If you know of a good link for this information, I would appreciate it. thanks.