ECDSA is a signature algorithm. SA at the end stands for it too: Elliptic Curve Digital Signature Algorithm.
Thank you, just to add something to that there is another algorithm that use Eliptic Curves to establish a shared secret between two pairs of keys ( public and private) :
Elliptic-curve Diffie–HellmanThis one allows to create a Shared secret that can be use used as KEY for Symetric Encryption bewteen Alice and Bob...