The are 3 basic types of construction of Photovoltaic solar panels although all of these use silicon.
Monocrystalline cells are cut from a single crystal of silicon. They are basically a slice of crystal. This makes them very smooth in texture and you will can see the thickness of the slice. Monocrystalline cells are the most efficient, but also the most expensive to produce. They are completely rigid and must be mounted in a rigid frame for protection.

Polycrystalline (or Multicrystalline) cells are made from a slice cut from a block of silicon, but whereas Monocrystalline cells are from a single crystal, these cells consist of a large number of crystals. This gives them a speckled reflective appearance but, once again you can you see the thickness of the slice. Photovoltaic solar panels made from these types of cell are slightly less efficient but also slightly cheaper than monocrystalline cells. They also need to be mounted in a rigid frame.

Finally, amorphous cells are manufactured by placing a thin film of amorphous (non crystalline) silicon onto a wide range of surfaces. These create the least efficient type of Photovoltaic solar panels but also the cheapest. Due to the amorphous nature of the thin layer it is flexible, and if manufactured on a flexible surface, the whole photovoltaic solar panel can be flexible. One problem with amorphous cells, however, is that their power output reduces over time, particularly during the first few months, after which time they are basically stable. The quoted output of an amorphous panel should be that produced after this period.