Every shard in Vitess uses normal MySQL replication to replicate changes from the master for that shard to the replica(s). Vitess can use asynchronous MySQL replication (the default), but can also be configured to use semi-synchronous MySQL replication for environments with higher durability requirements.
VReplication is used internally in Vitess for items like resharding, moving tables, and materialized views. It is not used directly to keep replicas in sync with a master.