Cacti are very popular and are grown both indoors and outdoors.
There are many types of cacti, which differ in size and color.
While some of the cactus plants have leaves, some others lack spines. Usually, the term cactus denotes plants with spines and succulent stems; but jungle cacti, which are natives to rainforests, lack these features. They are much different in their appearance and growing conditions. Hence, it is important to understand the type of the plant, before purchasing it.
Read more at Buzzle: http://www.buzzle.com/articles/how-to-grow-cactus.html