Why does it snow? If snow is simply freezing rain, then what is hail?

There are quite a few forms of precipitation

Sleet

(PL) - Sleet is defined as pellets of ice composed of frozen or mostly frozen raindrops or refrozen partially melted snowflakes. These pellets of ice usually bounce after hitting the ground or other hard surfaces. Heavy sleet is a relatively rare event defined as an accumulation of ice pellets covering the ground to a depth of ½" or more.

Freezing Rain

Rain that falls as a liquid but freezes into glaze upon contact with the ground.

Rain

Precipitation that falls to earth in drops more than 0.5 mm in diameter.

Snow

Precipitation in the form of ice crystals, mainly of intricately branched, hexagonal form and often agglomerated into snowflakes, formed directly from the freezing [deposition] of the water vapor in the air.

Hail

Showery precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter, falling from a cumulonimbus cloud.

You can use the glossary page to type any weather vocabulary words you are interested in here: http://www.weather.gov/glossary/

You can also browse through other weather topics here:http://www.metar.no/jetstream/matrix.htm

Snow is a form of crystallized water that forms in the atmosphere. Not freezing rain, which falls as rain and freezes on contact with objects that are at temperatures below 32 deg F. Sleet is another form of frozen precipitation which falls as rain but before it gets to the ground freezes and falls as usually small pellets of ice. Hail one the other hand is formed in thunderstorm clouds in the spring and summer typically. Rain is blown upward to such a high altitude that it forms balls of ice which can come in sizesfrom pea size to golf ball size or larger.

hail is clumps of ice. snow is flakes hence snowflakes.

if this helped plz give me the best answer :D