There's various lighting options with terrariums - some of the models we sell have built in lighting so they're ready to go, straight out of the box. On the other end of the scale are the smaller one's and these will need lighting for your plants to survive.
How much light do I need?
This depends on the plants that you are growing. Some need very little and some require a bit more. The plant labels will show you how bright the light needs to be.
Can I place it on a window ledge?
For smaller terrariums and if you're not investing in artificial illumination, I'd recommend you position them near a window but not on the ledge. Lighting is too intense for most plants there (unless you're choosing a succulent or cacti). Bright, indirect light is ideal and that means no direct sunlight to avoid scorching and fluctuating humidity levels.