Termite generally damage wooden articles like doors, window, bed, wardrobe etc. Termite eats wood and other cellulose items like paper etc. So they treat wood as their food and damage wooden items by eating. According to many studies termites damage billions of rupee wooden and other articles in India. Thus you can imagine how dangerous termites could be if they are present in your premise.
It is very difficult to detect termites in home because they reside mostly in the soil and deep inside the wall. Once they make any major damage then only it can be detected generally.
If you pay attention on small things around the house, then it can be detected easily like if you find swarmers on window sill and other place, there could be termite in your premise. Also if you find wings of swarmers around or inside house you should be alert about termites.