Terrariums are miniature landscaped gardens in a bowl. Its not just a matter of picking some plants and planting them in a fish bowl. There is an art into landscaping a miniature garden mimicking nature, may it be forest, a boo, a desert, a hill, a riverside, a waterfall or event front yard or playground, park etc.
What do you need? Apart from the usual plants, and soil and moss etc, one may need all the accessories like miniature figurines, miniature logs of wood, rocks, trees, waterfalls, lakes (these can be artificial). Here are some examples of what can be used. If you would like to add some miniatures, they can be purchased from here