Termites feed primarily on dead wood and wood by-products. Once termites have started eating on your house they will continue to consume it as fast as they can. Although it can take months or even years before the damage from termites is visible, a healthy termite colony can consume a foot of two-by-four in just a few months.
Since they tunnel into the wood this damage is usually spread out. They will eat anything made from wood including furniture, books and new wood. The most important thing when you discover that you have termites is to take the proper steps for fixing termite damage and preventing any future infestation.