I see termites a lot. When I am splitting wood for my wood heater I find them in the wood. It is a natural part of the process of the decomposition process of wood that has been in contact with the ground. The termites consume the wood and return it to the soil. In nature it is a good thing. When they get into the wood in your home it is bad. They can destroy a board in just a few days. If left alone, they will move from the first board to the next and beyond. They are very sneaky in their approach. Termites need water and they need food. If they have both then there is nothing to stop them from destroying a home. We use pressure treated lumber in areas that are exposed to the elements and/or the ground. The treatment in the lumber makes it undesirable as food to the termites. We also use masonry products such as block or brick in areas that contact the ground. This is a good deterrent to the destructive bugs.