You might see split ends if you look carefully at the ends of your hair. You'll see a single hair that has literally split into two at the bottom of the strand.
Split ends can be caused by repeated blow-drying, heat-straightening, or excessive brushing. Once your ends are split, the only solution is to go to the salon to get them trimmed. But you can avoid split ends by brushing less, using less heat on your hair, regularly using conditioner, and protecting your hair from extremely hot or cold weather.
WebMD Reference: Hair Care Tips for Teens.