Inverted pyramid refers to the structure or model commonly used for hard-news stories. It means that the most important, or heaviest information goes at the top of the story, while the least important information goes at the bottom.
Here's an example: He used the inverted pyramid structure to write his news story.
The inverted pyramid format was developed during the Civil War. Correspondents covering the great battles of that war would do their reporting, then rush to the nearest telegraph office to have their stories transmitted, via Morse Code, back to their newsrooms.
But the telegraph lines were often cut in mid-sentence, sometimes in an act of sabotage. So the reporters realized they had to put the most important facts right at the very start of their stories so that even if most of the details were lost, the main point would get through.
(Interestingly, the Associated Press, which is known for its extensive use of tightly written, inverted pyramid stories, was founded around this same time. Today the AP is the oldest and one of the largest news organizations in the world.)
Inverted Pyramid Today
Of course, some 150 years after the end of the Civil War, the inverted pyramid format is still being used because it has served both journalists and readers well. Readers benefit from being able to get the main point of the story right in the very first sentence. And news outlets benefit by being able to convey more information in a smaller space, something that's especially true in an age when newspapers are literally shrinking.
(Editors also like the inverted pyramid format because when working on tight deadlines, it enables them to cut overly long stories from the bottom without losing any vital information.)
In fact, the inverted pyramid format is probably more useful today than ever. Studies have found that readers tend to have shorter attention spans when reading on screens as opposed to paper. And since readers increasingly get their news not just on the relatively small screens of iPads but on the tiny screens of smartphones, more than ever reporters must summarize stories as quickly and as succinctly as possible.
Indeed, even though online-only news sites theoretically have infinite amounts of space for articles, since there are no pages to be physically printed, more often than not you'll find that their stories still use the inverted pyramid and are very tightly written, for the reasons cited above.
Do It Yourself
For the beginning reporter, the inverted pyramid format should be easy to learn. Make sure to get the main points of your story - the five W's and the H - into your lede. Then, as you go from the start to the finish of your story, put the most important news near the top, and the least important stuff near the bottom.
Do that, and you'll produce a tight, well-written news story using a format that has withstood the test of time.