is it another technique for adding detail or something?
Yes exactly .
Some people like adding detail this way . I think you can even create custom brushes to add texture directly to the mesh … I haven’t tried it myself in the RC versions of Blender yet but I have tried SharpConsruct by the guy who added it to Blender . It lets you play with the mesh as a kind of “digital clay” . Kind of tedious to work that way for my taste but lots of people seem to like it (hence the popularity of Zbrush). Also you need higher end systems to get the higher resolutions for the detail as well …
Oh, and start with a mesh that has a lot of vertices. Scluptin the basic cube will not do much. Subdivide it four times, set your brush to be small, and you will have a lot of fun.