The Stellar network is a distributed blockchain based ledger and database that facilitates cross-asset transfers of value, including payments. The native digital asset of Stellar is called Lumens (XLM)
One lumen is a unit of digital currency. While you can’t hold a lumen in your hand, they are essential to the Stellar network—they contribute to the ability to move money around the world and to conduct transactions between different currencies quickly and securely.
White Paper / Documentation