They are made of solid ice. Some have smooth surfaces. Others have raised designs on their surfaces. The design is the same on each side of the snowflake. These are very tiny snowflakes.
Equilateral triangles are triangles whose sides are all the same length.
Six equilateral triangles can be tessellated in a regular hexagon. The word tessellate means to cover a space completely with shapes in such a way that there is no uncovered area left in the space.