A terrarium is an enclosed or partially enclosed structure made of glass or transparent plastic for growing plants and sometimes housing small animals. Often the plants and animals have specific needs that require carefully controlled conditions.
These are completely sealed off from the outside and ideally should not be opened at all. It is very difficult to perfectly balance the micro-system, but they require no care beyond that when done correctly.
These terrariums are often not completely enclosed or have an easy-to-open door for access. They require regular care. Feeding of animals, trimming plants, and periodic watering and cleanup are needed.
Small ferns, mosses and bromeliads are good plants for a terrarium. They benefit from the high humidity and often do not require much soil.
Some small frogs, snakes and turtles require a natural feeling habitat of a planted terrarium, and benefit from the high humidity and controlled environment.
With lower light-loving plants, a bright room might be sufficient. Higher light-loving plants might need a supplemental light. Avoid any direct sunlight as it builds up too much heat.