The difference between a coach and a mental health professional
Licensed mental health professionals have received advanced postgraduate training in how to recognize different forms of psychological distress and to intervene using scientifically validated methods. They are required by law to uphold ethical standards (which they can be held accountable for breaking) and to remain abreast of advances in knowledge. The requirements of their licensing are usually rigorous and carefully monitored. This sets them apart from coaches and lay or volunteer counselors, who are often unregulated and might not meet similar minimum standards.
Remember that each country (or state) defines its professional categories and their educational requirements differently. Feel free to research the requirements in your region (and abroad) and to ask professionals if they hold valid licences that verify whether they have met these. Not all professional titles are regulated everywhere. If you choose to see someone who claims an unregulated title, ask them about their training and compare their answer to the requirements in other regions.