Wikipedia
A splitboard is a snowboard that can be separated into two ski-like parts used with climbing skins to ascend slopes the same way alpine touring or telemark skis are. The two halves can then be connected to form a regular snowboard for descent.
When snowboarding originated, it was often prohibited on pistes (established ski trails). Early snowboarders sought out pristine snow conditions as a necessity. The development of splitboards has simplified backcountry snowboarding where pristine powder snow is more likely to be found. Splitboards address the inherent weakness of snowboards of having limited backcountry range away from lift systems. This weakness stems from snowboard riders having both feet fixed to a board, so a standard snowboard can't climb up hills the way skiers can.
Splitboarding started in the mid-1990s and has grown in popularity. In 1991, Brett "Cowboy" Kobenik brought a crude prototype of the first splitboard to Mark "Wally" Wariakois, the founder of Voile. At the time Wally was intensely focused on innovating new backcountry ski and telemark binding designs, but he saw the future of backcountry snowboading in Cowboy's crude design. Over the next few years, Cowboy and Wally refined this idea and in 1994 released the first DIY Voile Split Kit. This was the beginning of the splitboard revolution. For the first time riders had a truly innovative and easier way to access backcountry powder. Some companies have begun making splitboard specific bindings. These bindings are designed to reduce the weight associated with the adapter plate/standard binding combination. The reduced weight increases the range and duration of extended uphill climbs. The binding's lower foot bed also increases board feel.