Root beer was traditionally made from sassafras root, but they have long used chemistry to mimic the taste. Root beer is easy to make if you have home brewed beer or wine - the equipment is the same. It is a dark, cola-looking soft drink or soda but has a slight bite to the taste but is smooth like cream and spices like clove, nutmeg and cinnamon. It is pretty pleasant to drink, especially the good stuff. Most mass produced root beers are a shadow of the real thing, thus this topic.
Reminds me of a good story....
Friends of mine (older than I) were hosting an exchange student from Slovakia whose idea of soda extended to coca-cola and nothing else. They all go visiting friends of theirs and he's offered a root beer (get the foreigner to try something new). He takes one sip, literally spits it out and in his heavy accent exclaims, "What the hell is this ****."
Apparently other Eastern Europeans frown equally on the taste.