MBI stands for Mindfulness-Based Intervention - a structured, typically 8-week group program built around mindfulness practice. There isn't just one; over the years the field has developed several, each adapted for a different focus (stress and pain, relapse prevention, self-compassion, and so on) while sharing the same basic structure. MindfulCertify currently supports MBSR, MBCT, MBC, MBRP, MBCP, and MSC - see
Programs for what each one is and where it came from.