Canon makes several series of non-SLR digital cameras; each line of cameras begins with a letter-number designation. The A series is the entry-level tier; they're the least expensive but they also lag in features. The Sx00 Elph series is the most compact. The S and SX series is mid-tier—larger and more powerful. The G series is the top: it has a lot of the EOS features but lacks interchangable lenses.
One of my mother's later digital cameras, and a step up from the A-series point-n-shoots that she had been using. The IS stands for Image Stabilization, which is needed to support that big zoom.
Among other nice features, the LCD screen is on a swivel panel so you can flip it around and view it from conveient angles. Another nice camera that got worn out from heavy use.