Who are this people in white, often attend to monks?

I attended a dhamma talk last month by a Thai monk but English translation were also provided on site. There was this westerner who is giving English translation but may not look like a full time monk? Although he was in white shirt, partial shaved head, but doesn't seem like wearing a rope. Was wondering, how would they be addressed as in monastery? Or they are just layman working for the monastery? Thanks. Sadhu sadhu sadhu