A split end begins as a tiny lengthwise crack in the outer layer of the hair shaft; the crack eventually penetrates deeper into the shaft, splitting it completely.
There are numerous protein conditioners on the market that can provisionally repair hair that can provisionally repair hair that has split or frayed at the ends. These products contain proteins that are sticky, and they act like a temporary adhesive, holding the split ends together for a few hours. In addition, the proteins in these conditioners help to coat the individual hair shafts and fill in damages areas. The only way to eliminate split ends altogether, however, is to have them cut off.
Careful grooming, including gentle brushing and combing, and avoiding teasing and excessively hot hair hot hair dryers and curling irons will also reduce the chances of your hair splitting. The best solution, of course, is to wear your hair short, so that split ends will be less likely to occur in the first place.