National Geographic is the common name for the magazine of the National Geographic Society, which has been published regularly for some 121 years, and is by far the United States' most popular general interest academic magazine. In fact, there isn't really another magazine that does what National Geographic does: while there are science magazines, travel magazines, and current event magazines, only National Geographic combines all of these functions and more into a magazine that can travel up and down the width and breadth of human knowledge. They are also notable for their distinctive yellow border and square binding, which means that they are sturdier than most magazines, and copies of the magazine going back to the 1950s are still available hidden away at yard sales and thrift shops.
The format of National Geographic has remained remarkably consistent over the years, at least as far back as I have seen copies. The magazine will have a number of articles, usually spread out broadly across the academic disciplines. While the "Geography" of the title is the unifying factor, it may mean the geography of a small city, or the geography of the solar system. The articles are distributed fairly evenly between those that describe natural sciences, such as describing an ecosystem, and those describing human social or political groups. While not a news magazine as such, often the articles do discuss areas that are of relevance to current events. The magazine also is usually lavishly illustrated. Of course, as time has gone by, the definition of "lavishly illustrated" has increased, with issues in the past decades being full of two page and fold out spreads showing panoramas of natural wonders.
Also, I couldn't complete my description of National Geographic without mentioning the endless titillation it provided generations of pre-internet youths with glimpses of nudity in the way of topless indigenous women.
Overall, National Geographic is in an unparalleled place as far as popular magazines go, offering generations of people a look at parts of the world that they will probably never get to go, and might not even know the existence of. As a youth, I obsessively collected National Geographics, and got a basic picture of the world by reading through them.