This video from Kahn Academy describes, with drawings and a mini lecture, the intrusive thoughts and rituals of OCD.
Sizemore, T. A. (2010). Free from OCD : a workbook for teens with obsessive-compulsive disorder. Oakland, CA: Instant Help Books.
Teens can learn to use cognitive behavioral exercise to combat intrusive thoughts and repetitive actions using this workbook. The exercises can help teens break the habit of performing rituals (which give a false sense of control) and free teens from feeling trapped by OCD.
What is Obsessive Compulsive Disorder (OCD)? by Khan Academy (2016)
Lots of people may casually joke that they suffer from this problem, but this article from Khan Academy explains the terrible feelings and symptoms associated with this disorder.