CD's play from the inside out.There are areas called pits (self explanatory holes) in the plastic and the non pitted areas are called lands. A laser reads these pits as data, different depths are different data. A vinyl record uses a stylus to cut a disc, the vibrations of sound cause the stylus to vibrate and cause little bumps to be cut in the groove in the master disc. This is then reproduced and pressed as a record.
Also, the RPM changes for CDs. Get a CD with a long play time and you should hear a difference between revs on the first track (fast) and the last track (slow). This, I assume, is to keep constant rate of input when the laser is scanning different areas of the disk. I believe vinyl players have a constant RPM (though I stand to be corrected!).