What is birch beer?

According to Wikipedia:

"Birch beer is a carbonated soft drink made from herbal extracts, usually from birch bark. It has a taste similar to root beer. Various types of birch beer are available, distinguished by color. The color depends on the species of birch tree from which the sap is extracted (though enhancements via artificial coloring are not uncommon)"

The most common type of birch beer is dark in color, made using oil from the black birch tree.