A lick of licorice
Anise and star anise are not the same spice, nor are they related species despite the similar name and flavor profile. They do both contain the organic compound anethole, which gives them their similar licorice flavor.
Fennel is another spice that contains anethole. It is a seed that is often confused with anise—due to its similar flavor profile and also to its similar appearance. Fennel seed is considerably larger and often brighter in color than anise seed. Anise seed, in addition to being smaller, also tends to have a small bit of stem "tail" attached to one end; whereas this happens only occasionally with fennel, it is much more frequent in anise seed.
Since anise seed is more expensive to produce than star anise, star anise has surpassed anise in production for anethole extraction and for commercial use in flavoring food products. Anethole is reputedly multiple times sweeter than sugar with the distinction of having a pleasant flavor at higher concentrations.
Use this pungent spice sparingly. If used whole, chewing will release more complex flavor in your dish.
Anethole, the aromatic compound that gives anise, star anise, fennel and licorice its flavor, is highly soluble in alcohol but not very soluble in water. Drinks that combine anise-liqueurs with water or ice will result in cloudy liquid called the ouzo effect.