Vlogs are video blogs. The vlogs I have posted here are music vlogs which are used to talk about music, music videos, performance etc. However, vlogs can be used for many other things, such as, personal updates, lifestyle, and fashion, to name a few. Vlogs can promote artists and their music videos, in this case the blog at the top inadvertently promotes Britney Spears' music and videos as the viewers of that video may then go on to search those songs/videos, increasing the number of views for Britney Spears. The second video is about Rock music vlogs, this vlog doesn't promote any artists but it does promote 85 other Rock music vlogs which will promote the songs and video they choose to talk about.