Mount Etna is here because the tectonic plate of Europe (carrying mainland Italy and Sicily) is colliding with and overriding the African plate. The African plate is peeling away from the surface and descending deep into the earth, where water in porous rock and hydrated minerals is forced out. This causes the overlying (European) rock to melt and rise, until it collects in a pool of magma near the surface. The drop in pressure enables gas to bubble out of the magma, until the mixture of gas and magma eventually erupts through the surface. This has been happening continually on Mount Etna for some 500,000 years, with multiple layers of lava and ash building up into a mighty stratovolcano.
Mount Etna has been more active since the start of the 20th century, and even more so in the 21st. Its height is about 3329 m or 10,922 feet (as of 2007), but it's constantly being remodelled by eruptions from the five summit craters. These are usually spectacular but only destructive to the immediate vicinity. But there also dozens of side-vents lower down the flanks of the mountain, which sometimes erupt close to human habitation.
Reluctance to settle too near has preserved the natural wildlife and habitat, ranging over several climate zones. The whole area is a Nature Reserve, and is inscribed on the UNESCO World Heritage List. The area is a ski resort in winter. Come dressed for the cold even in summer.