What is the difference between obsessions and compulsions in OCD?

Obsessions are persistent, unwanted, intrusive thoughts, images, or urges that cause significant anxiety or distress. Common obsessions include fears of contamination, harm to self or others, symmetry, and forbidden thoughts. Compulsions are repetitive behaviors or mental acts performed to reduce the anxiety caused by obsessions, such as excessive handwashing, checking, counting, or arranging. The compulsions provide temporary relief but reinforce the cycle because the person learns that the ritual reduces anxiety.