Semi Leaven Breads have many aliases - 'yeasted sourdough' breads, 'pre-fermented' breads, 'time dough' breads, 'artisan' breads, 'semi sourdough' breads - and there are many others. I've always referred to them as 'semi leavens', because they are part sourdough (leaven or levain) and part yeasted breads. A fully leavened bread, therefore, would include regular sourdough, by this terminology. Just in case you were wondering.
Semi Leaven breads also can take on any texture - you can make very light breads with this method, or loose textured continental style breads, and even rich and full flavoured wholemeals.
Because of the faster fermentation, crusts can be baked to be either quite thin (which can be hard to do with regular sourdough) or thicker. You can also use the method as a 'shortcut to sourdough' technique, for times when you don't have a lot of time. In every baker's life, too, there are times when the poor old leaven just isn't up to the task. Again, a little yeast, and away you go..
Surefire success follows.