We frequently say we're "obsessed" with this or that in our daily conversations. However, what we really mean is that we are passionate about something or ruminating about something.
A true "obsession" is an intrusive, recurring thought, image or impulse considered to be inappropriate and/or irrational while most likely causing some degree of suffering. Obsessions are not typical concerns over stress in relationships or career.
They can manifest in many different ways, but some common obsessions are fear of germs or of being contaminated, fear of causing others harm (stabbing someone, hitting someone with your car) or of harm coming to oneself, inappropriate sexual thoughts (ex. incest), violent images, numbers, fears of being gay, etc..
Obsessions are the hallmark of Obsessive-Compulsive Disorder (OCD). The other is compulsive behavior meant to undo a specific obsession or anxiety.
