This type of water transition or change in phase of matter is known as FREEZING.
Water has molecules that are free flowing and have the ability to collide and bounce against each other, that's why it has that kind of characteristic that it takes the shape of its container.
When these molecules are exposed to lower or colder temperatures, the molecules tend to vibrate and get attracted towards each other, creating a semi-solid or completely solid material. In this example, liquid turned into frost because of the low temperature present within the environment.
Both ice and snow are basically frozen water however the difference lies in their composition. Snow is regular shaped crystal form while ice is solidified sheet of ice.
When the temperature has fallen below 32 degree Fahrenheit, the vapor in air converts to snow and falls on earth. The different shapes of snowflakes depend on the freezing temperature. For example at temperature below 30 degrees, snowflakes are thin, hexagonal plates while at temperature lower that 25 degrees the snowflakes are needle shaped.
When snow lands on the earth, they remain in their crystal form and starts depositing layer by layer. However, these snowflakes melt partially and then get refrozen due to which space between the crystals is filled with water. This process of deposition continues till ice is forms.
