To almost any photographer today, if you mention "APS," they think of crop sensor cameras, namely APS-C or perhaps the APS-H sensor in older models in Canon's 1D line. However, if you mentioned it two decades ago, the response would have been very different.
Coming to you from DPReview TV, this great video takes a look at the APS film format of yesteryear. APS ("Advanced Photo System") was a film format introduced by several manufacturers in 1996 that sought to both streamline the amateur photography experience and give it more advanced capabilities. Such capabilities included three image formats (16:9, 3:2, 3:1), an innovative cartridge that could be removed while in the middle of the roll (think of swapping out different ISOs without having to waste frames to get to the end of the roll), and the ability to record advanced information about an image. I owned a translucent blue Kodak Advantix F310 camera that my mom got me for class trips, and I remember how the different crops inspired my eighth-grade creativity quite a bit. Unfortunately, the digital era brought the end of the format, but it still makes for some very interesting photography history.
Lead image by Wikipedia user Aaronyeo, used under Creative Commons.