Ice: it's just water, but much colder, harder, sharper and more slippery than water in its liquid or gaseous states. Ice has a crystalline structure, which is responsible for the hardness and sharpness. This crystalline structure is much more evident as frost and snowflakes when ice forms from very tiny droplets suspended in the air or directly from water vapor.
About 2% of all the water on Earth is frozen, and this percentage varies very little throughout the year because around 99% of all the freshwater ice on Earth is contained in the massive glaciers of Antarctica and Greenland, which have an average depth of more than a mile. Snow can cover up to one-third of Earth's land mass during the northern Hemisphere winter, but this layer is relatively very thin and contains only a tiny portion of Earth's water.