In normal crystalline solids, molecules or atoms sit in fixed locations, arranged in a pattern which repeats itself over space. In normal liquids, the molecules are free to move about, and their distribution over space is not point-like but smeared and more or less uniform.
Liquid crystals are states of matter intermediate between normal liquids and normal crystals.
In smectics, the molecules again lie in parallel layers, though they are free to move about within each layer, but now are oriented perpendicular, or nearly so, to the layers. These are the principal sorts of liquid crystal, but literally dozens of distinct phases have been identified.