what should I do to synchronize the tables of users and access levels of two sites in two different servers with the same system

I do not want to do every time export and import again. If someone registered on first site, no need to register on the second site, what should I do?
I want only tables of users and access levels are synchronized with each other and others of the tables don't change

Synchronize and Replication is suggested, how different are they? Which method is proposed and how is its performance?
The database is MySQL.