For some it may be something as simple as remote or automatic control of a few lights. For others, security may be the central application. Still others may choose to install advanced controllers or use voice recognition. As a very basic definition, home automation is anything that gives you remote or automatic control of things around your home.
Remote control gives you the convenience of controlling lighting, appliances, security systems and consumer electronics from wherever you happen to be at the time like your couch, car or even in your bed. There are several different "methods" of controlling devices remotely: Infrared IR, Powerline, Radio Frequency RF, Insteon and Hardwired.
X10-compatible products are the most popular home automation products because of their low cost and ease of installation, especially into existing homes. X10 is a communications "language" that allows compatible products to talk to each other using the existing electrical wiring in the home.