A Crystal is a particular type of solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered array extending in all three spatial dimensions. Various shapes of crystals are found in nature, and are dependent on the types of molecular bonds between the atoms to determine the structure. Snowflakes, diamond, and common salt are examples of crystals.
In a household context, crystals (short for lead crystals) refer to glass items made with lead added in the manufacturing process. Despite the confusions with its name, lead crystal or any form of glass is an amorphous solid. Some classify glass as a supercooled liquid.
Liquid crystals occupy a conceptual middle ground between the crystalline and the amorphous--they exhibit order in some dimensions, but amorphous-like disorder in others.