Clips and spacers are different types of beads that play quite valuable parts in a bracelet. They are used to even out or put space between your decorative beads on your bracelet. Clips are the type of beads that act like clamps which you can fix on the threads of your bracelet. If you wish to divide the pattern or decoration of the beads, then clips are the way to go because they prevent other beads from encroaching into another portion of your bracelet.
Spacers are little beads which thread into your bracelet, but they are not fixed. They are generally used as subordination to your overall design, to give importance to the bigger beads. They also leave space to even out the designs and provide additional patterns that may look nice on your bracelet.