People with OCD have unwanted and intrusive thoughts, images, or impulses called obsessions that repeatedly enter their minds. They also have unwanted feelings of angst that keep on intruding into their lives. The series of worrisome thoughts and feelings lead to behaviors they feel the need to do repeatedly called compulsions.
Compulsions are often a way of trying to neutralize or gain control over the obsessions. For example, in the previous example, someone suffering from an obsession with contamination may wash their hands excessively or avoid touching door handles. Unfortunately, the compulsions take up a lot of time and get in the way of leading an everyday life.