Traditionally articles in newspapers were written in the inverted pyramid (or front-loaded) style. Using this technique the most important details are included in the first paragraph, with further information and specifics added later on.
The purpose of loading the important information at the top was two-fold; people skimming the article could get the important information quickly, and decide if they wish to read further, and the editor could cut from the bottom up if there wasn’t enough space on the page for the entire article without fear of cutting out an important detail.
While the second use is less important in electronic media, the first is even more important as the digital audience is even less likely to want to read an entire article to get all the facts.
Image from http://www.cybercollege.com/frtv/newsp2.htm
See three examples at http://www.jprof.com/2013/05/28/inverted-pyramid-news-story-examples/