Legend has it that a unicorn can only be tamed by a virgin, the first one being the virgin Mary.
They are said to be experts at hiding, and to have the ability to cure poisons.
In Art Unicorns first appear in medieval times. Religious art was popular at this time and unicorns were mentioned in the King James Bible. They were used regularly in heraldry, coats of arms and tapestries. Many of these the unicorn bears greater resemblance to a one horned goat or deer then the popular horse with a single spiral horn. The art often depicted the hunt of the unicorn or its seduction of the unicorn by a virgin. They are white with a a lion like tail and usually cloven hooves. In modern times unicorns are popular fantasy creatures for artists. The most common version is a white horse with a single spiral horn. This white horse may be of an arabian type with a dished face or the andalusian type. But being a fantasy creature, there are no hard and fast rules. A unicorn can be any color, any style. They may have cloven horns, beards, and a lions tail. You can view the Unicorn Tapestries here: The Met Museum Unicorn Tapestry Exhibit
Body Types: Popular types include goat, deer and horse. Occasionally a unicorn may be like a donkey. Within the horse types there are the heavy swamp type such as the clydesdale, the andalusian type, the arabian type. There is no limit color.
Symbolism: Unicorns usually stand for purity and chastity. But they are also fiercely independent. Legend has it that the unicorn can only be tamed by a virgin. The symbolism is heavily Christian, but in all cultures the Unicorn is considered a sign of good fortune.
Origins may come from all or part of these. The ancient Greeks believed Unicorns were natural creatures that hailed from India. The King James Bible also mentions Unicorns. Single horned goats - this comes from a vision of Daniel in the Bible, and it's easy to imagine that a genetic mutation of a normally two horned species could lead to unicorns. There is a species of whale known as a narwhal that has a single spiral horn. Rhinocerous also have only one horn, although they hardly fit the graceful legend.
The most famous Unicorn book is The Last Unicorn, by Peter S. Beagle.
Others include: The Unicorn Chronicles by Bruce Covelle,
Unicorns of Balinor by Mary Staunton.
The Firebringer Trilogy by Merideth Anne Pierce
In Movies The Last Unicorn has an animated version.
The movie Legend starring Tom Cruise features two unicorns whose survival affects the fate of the forest.