Sugar paste (also known as as sugar gum or gum paste) is a sort of sugar dough used in pastry-making to cover cakes and/or to create cake decorations. Since it is made with sugar and glucose, it is white, but can be colored.
This dough is very versatile and can be used in very original ways: it is all up to your imagination. Nowadays you can easily take cake decorating classes to learn the best techniques to make plain cakes more visually interesting.
Beside its longer shelf life, the undeniable advantage of the commercial version of Sugar Paste is that it is very elastic and easier to manipulate and model.
Here you have a few examples, with tutorials: