I believe it is reindeer moss(Cladina rangiferina) which is really a lichen or combination of fungus and algae. It should do well in a closed terrarium but I have no experience with it. It is a really beautiful lichen and I would like to try it in one of my creations this spring. Let me know how it goes if you try it please!

Hi ... i've tried growing Reindeer Moss. It needs air circulation and won't last long in a closed terrarium. I've tried growing it under fluorescent lights and a south-facing window. I was able to keep a jar of it going for a few months with frequent spraying with distilled water. But eventually it died.

If anyone knows how to keep it alive, i'd be interested in learning about it too.

Since the image has been removed I cannot say that the image was this Cladonia since this is an Artic species.
But speaking of lichens in gerneral.
To grow them you need a very cold spot to set them in.
Inside a terrarium is ok if you can ventilate it.
My experience with lichens is that they need it cold and tend to do well with dry feet but appreciate being watered or sprayed regularly during the day every day.
Their greatest enemy are snails and slugs which can eat out a whole colony. Moist humid shade with cold air and good air movement seem important.