All honeys are liquid when taken out from the hives and all honeys crystallize at some point. But how long the crystallization takes to happen, few weeks, few years or few decades depends on where the bee has collected the nectar from. To be specific the fructose level of the origin plant determines how quickly the honey crystallizes.
Liquid honey: Naturally liquid honey stays liquid because it has been collected from specific kind of plants. But no honey stays liquid forever and over time starts to crystallize.
Crystallized honey: Crystallized honey has also been liquid when taken out from the hive but has crystallized before sale. Most of the plants in Finland produces the type of nectar that crystallizes quickly
Liquid honey is best to store in room temperature approximately + 24 °C . If liquid honey is stored in cold it starts to crystallize quicker. Usually the formation of crystals starts from the sides and bottom of honey jars and bottles. Crystallized honey is perfectly good honey but if you want the substance back to liquid you can liquefy the crystals on low temperature. The honey bottle or jar can be placed in warm water about +40°C even for few hours if heavily crystallized. Honey is not recommended to be liquefied in hot temperatures as overheating destroys the beneficial enzymes.