A mindfulness teacher teaches mindfulness practice, usually delivered as an eight-week group course, for people who want to manage stress and improve their attention day to day, rather than to treat a diagnosed illness through a formal clinical process.
A different thing from a similarly named clinical treatment
This is worth distinguishing clearly from mindfulness-based cognitive therapy, which is a specific clinical treatment for recurrent depression, delivered by a trained clinician and grounded in a defined evidence base for relapse prevention. A general mindfulness course and a clinical MBCT programme share underlying techniques but are not equivalent in scope or purpose.
Checking training, and when caution is needed
Mindfulness teacher is an unregulated title in the UK, and the BAMBA register is the recognised UK marker of proper training in this field, worth checking before joining a course. It is also worth knowing that intensive meditation practice is not suitable for everyone, and is generally not advised during acute mental illness without clinical support already in place alongside it.