The pale, springy, branching stuff sold by the bag for moss walls, floristry and model scenery goes by the name reindeer moss, and like the marimo it is misnamed. It is a lichen.
Not a moss
Reindeer moss is Cladonia rangiferina and its relatives, lichens rather than plants: each is a partnership between a fungus and an alga living as a single organism. That is why it feels dry, brittle and cartilaginous rather than soft and leafy, and why it is grey-white or pale green rather than the fresh green of a true moss. For how to tell the groups apart in general, see moss, lichen, liverwort or algae.
In the wild
In the tundra and on northern heaths it forms vast pale carpets, and it is a winter mainstay for reindeer and caribou, which dig it out from under the snow. It grows extraordinarily slowly, often only a few millimetres a year, so those carpets represent decades of growth and recover painfully slowly once grazed or stripped. That slowness matters when it is harvested commercially.
The preserved decorative form
Almost all the reindeer moss you can buy has been preserved, its structure stabilised with glycerine and usually dyed a vivid green, so it stays soft and pliable indefinitely without water or light. In that state it is the workhorse of preserved moss walls, wreaths, terrarium dressing and model railway scenery, valued for its fine springy texture. It is no longer alive and needs no care beyond keeping it out of direct sun and damp; there is more on this use in preserved moss walls.
Can you grow it?
Not really, in any practical sense. Lichens this slow do not lend themselves to cultivation, and there is no quick way to raise a crop, which is exactly why the harvested wild supply raises sustainability questions. If you forage a little for a project, take sparingly and from abundant ground, knowing that what you pick took many years to grow and will take many more to return.