Monocrystalline solar panels are created using a single crystal silicon structure. This is the oldest solar panel technology. They are slightly move efficient than polycrystalline but also more expensive, and this begins the footprint size versus total cost debate.
Polycrystalline solar panels are produced using techniques that create many crystals within panel. They are currently the most affordable type of solar panel but product slightly less output power and thereby require more panels for a similar power output.
Since 1839 when Alexandre Becquerel first observed the photovoltaic effect, solar voltaic technology has been advancing and improving. New silicate structures, material advancements, flexible and wearable products, and reductions in the cost per watt continue unabated.
This is the most common type of solar panel for both residential and commercial building applications. Usually these panels are 66" by 40". Output power varies based upon the underlying technology, however typically they are ~300 watts.
Large scale photovoltaic projects use the largest size solar panels available to reduce both the number of panels and the installation cost. Most of these large scale projects use 72 cell panels which are 77' by 40". The power output can be as great as 400 watts.
Many many different sizes and shapes of solar panels are available to address many solar power applications. Emergency, recreation, travel, remote locations, charging, lighting, and many others. The multitude of uses for solar power are almost endless.