The Glideshow in Adobe Spark
"Turning words and images into ravishing, magazine-style web stories. Eye-catching layouts and themes will make you stand out from the crowd and engage your followers as it adapts to any device, creating a delightful read on tablets, smartphones or laptops." (Source)
"Your text, photos and videos instantly come to life with fluid, elegant motion. We call it a Glideshow. Your audiences will call it amazing." (Source)
Simply put, Glideshows allow you to layer other features on top of a picture or multiple pictures. The background images in your glideshow will fade into each other while other content scrolls through as you scroll through the glideshow.
Check it out! Penn State's Media Commons Guide to Glideshow Creation