Telehealth is the use of telecommunication technologies and electronic information to provide care and facilitate client-provider interactions. It is comprised of two forms:

1. Two-way, synchronous, interactive client-provider communication through audio and video equipment (also referred to as telemedicine)
2. Asynchronous client-provider interactions using various forms of technology

Serious mental illness (SMI) is defined as a mental, behavioral, or emotional disorder among adults aged 18 and older resulting in serious functional impairment, which substantially interferes with or limits one or more major life activities.

Substance use disorder (SUD) is a diagnosis that applies when the recurrent use of alcohol or drugs causes clinically significant impairment, including health problems, disability, and failure to meet major responsibilities at work, school, or home.

Co-occurring disorder (COD) refers to the coexistence of both a substance use and mental disorders.