$SAND can be used for several exciting things.
$SAND is the medium of exchange in The Sandbox's ecosystem. It will be necessary for making purchases from The Sandbox's marketplace. It will be required to purchase:
GEMs and CATALYSTs
$SAND holders will be able to participate in the governance of The Sandbox's platform.
Voxel artists will need $SAND in order to upload their voxel creations to The Sandbox's marketplace to sell in order to monetise them.
$SAND is also used for staking. In return, stakers will earn rewards, such as highly coveted GEMs and CATALYSTs.
Some games on The Sandbox's platform will be free to play (F2P). But not all of them. The game designer may choose at their own discretion to charge players a small amount of $SAND in order to play their games.
Players can potentially earn some $SAND by playing games. Simple as that.
You will be able to use $SAND to hire game designers and artists to collaborate on projects with you or commission them to design ASSETs for your project.
Some game designers may choose to give $SAND away as a reward in contests hosted on their LAND.