Claim Reward--> VEST, what are those?

Hi steem family,
I received 852 VEST as part of the infamous Claim Reward system but nobody seems to know what are they, where are they stored or how to use them (at least in the Spanish community)
Would any one put some light in my mental darkness?? Thanks
Acabo de darme cuenta que he recibido 852 VEST como parte de un Claim Reward pero no tengo ni idea de lo que es, ni para que sirve:
** 2 days ago Claim rewards: 0.061 SD, 0.054 STEEM, and 852.112553 VESTS**

¿Alguien puede poner un poco de luz en esta oscuridad mental mia??

Gracias majos y Buen día