Art therapy is a therapy session facilitated by a mental health service provider (e.g., psychologist, counselor, etc.) who may be trained in different expressive art mediums and encourage their clients or service users to reach their emotional, creative, and spiritual goals through different kinds of art-based exercises. 

Art therapy may be adjunct and integrated into other mental health interventions. The creative output invites the client or service user to examine their thoughts, emotions, and even body sensations throughout the creative process.

A Therapeutic art activity is not therapy. The goals of therapeutic art activities may include learning more about the art medium, practicing, and even experimenting with it. Engaging in therapeutic art activities may bring stress relief to the individual, hence being called therapeutic. These activities can be facilitated by anyone who has experience using the art medium of their choice but does not necessarily have to be a trained therapist.

For me in particular, I have more inclination and experience towards the visual arts (e.g., drawing, illustrating, painting, scrapbooking, collaging, etc.). :)