A central leader tree has one main, upright trunk with whorls of branches, usually beginning 60-90cm above ground, then again every 45-60cm up the trunk. The shape of a properly trained central leader tree is like that of a Christmas tree, where the lowest branches are the longest and the branches get shorter higher up the trunk. This allows maximum light penetration into the tree. 

Central leader tree training is recommend for apple, pear and cherry trees. 

Check out this video of how to get started with your fruit trees in a central leader form.