What is Stellar?

From:  https://www.stellar.org/

Stellar | Move Money Across Borders Quickly, Reliably, And For Fractions Of A Penny.

Stellar is a distributed, hybrid blockchain that is fully open-source. It is infrastructure that exists to facilitate cross-asset transfers of value, including payments. With just one integration into the Stellar Network, you will join an open, global financial network where all actors – be they people, payment networks, or banks – have equal access & economic participation.

The default currency of Stellar is called a ‘lumen’, which can be bought and sold on several digital currency exchanges.