The usual idea behind a terrarium is that the plants are housed in a sealed glass container so that they are in a closed environment which can look after itself. After the initial planting and watering the plants take up water from the soil and then exhale it from their leaves so that it runs back down into the soil again. So there is a continuous cycle and this is how the plants in the terrarium can be left to themselves. This video takes a different approach since these small terrariums are designed to be short term decorations for the Christmas holiday. So if you are looking for some inspiration watch the video below.
https://youtu.be/6kNqrvbe91I
