Article - Normal type, only displays in "Article Home" after the publication date.
Review - You will be able to add a rating to the article. Only displays in "Article Home" after the publication date.
Event - Used for showing upcoming events. Only displays until the "Publication/Event Date". This is the only difference from a normal article. Switching the type between article and event should cause it to appear and disappear from the Article Home page. (note: events are a 1.8 feature)