Most people make what is known as leavened bread - that is, adding yeast to dough in order to make it rise. The video is a time-lapse - 2 hours and 20 minutes of rising compressed into a 35 seconds of video. The dough is a mix of white flour and whole wheat (about 80:20 in this case). The yeast reacts with sugars in the flour, releasing CO2 in the process. This forms bubbles in the dough causing it to rise.
My apologies for the appearance of the bread loaves in this video - this was my first attempt at forming dough into loaves - obviously I need a lot more practice :-) The appearance didn't affect the taste.
For the technically inclined, the time lapse was done with a DSLR shooting still photos using a timer - one photo every 8 seconds. These still photos were then used as individual frames in the video.