Blog or Weblog
A weblog (often web log or blog) is a website which contains periodic, reverse chronologically ordered Posts on a common webpage. Individual posts (which taken together are the weblog) either share a particular theme, or a single or small group of authors...
in b2evolution a Blog is a kind of Collection. It is actually, the default kind of Collection.
See also: http://en.wikipedia.org/wiki/Weblog