That fright could be for a good reason, as termites often are present for one reason only, and that is to eat the available wood that constitutes the home. Well, first of all the pests themselves usually are completely hidden from view during their normal activities, and come to light only when an inspection of the hidden areas is performed, or damage is broken into and discovered during remodeling. Since the majority of termite species live in colonies in the ground it now is a mystery to you how to stop them.
Termites are insects.
The colony was started years ago by a Queen and King termite, that crawled or flew to that spot from some other colony, where they originated. Now, before we start to hate termites too badly, please understand their role in nature, and the importance of that role. Nature recycles everything eventually. Plants and animals eventually die - perhaps in several thousand years if it is a Knobcone Pine from the southwest desert mountains, or in just a few days if it is a little Mayfly. Even rocks are recycled, by water, lichens, animals, and other influences that attack the rock's structure, and this may take millions of years, eventually creating gravel or soil that is more useful for the growth of plants.