Ice forms when water freezes and turns solid. Snow is created when that ice forms crystals and falls from the sky. Though no two snowflakes are alike, nearly all of them have six sides.
Because it's solid with a crystalline structure, ice is actually considered a mineral. It's a mineral based on an atom of oxygen bonded covalently with two hydrogen atoms. Covalent bonding occurs when elements share electrons, instead of grabbing them from or giving them to one another. This gives ice many of its properties.
One property of ice is that it's less dense than water because of the way hydrogen bonds when the hexagonal crystals of ice are formed. Because of this, ice floats on water, which has immense consequences for the climate of the Earth.
Snowflakes are made when minuscule water droplets are super-cooled in a cloud. These droplets must get well below 0 degrees Fahrenheit for a snowflake to form. This is because water molecules or tiny bits of contaminants need to form a sort of nucleus for the snowflake to be built around, a process only possible at -31 degrees Fahrenheit.
Snowflakes can come in an amazing variety of shapes including rods, prisms, stars, plates, needles and columns.