Anxiety is one of the most universal human experiences. It consists of worry about the future, or about specific situations, as well as the physiological reaction to being in those situations (heart racing, sweating, and trembling, for instance). Stomach problems and difficulty sleeping are also commonly seen with anxiety.
As with most psychological diagnoses, it is considered a “disorder” only if it impacts the ability to engage in normal life activities. Psychiatrists may argue that those who have an anxiety “disorder” have some form of neurological difference that makes their experience of anxiety more extreme than others. However, no such neurological difference has been found. Some contextual situations in which anxiety can impact a person’s ability to engage in life include open places with many people (agoraphobia), parties or other social events (social anxiety), and particular triggers like spiders or needles (specific phobia). There is also a term for overall constant worry in many situations: generalized anxiety.
Panic attacks are sudden physiological reactions that are generally related to over-awareness of bodily sensations and a related worry about health (for instance, noticing your heart racing leads to worry about heart attacks, which leads to faster heartbeat, sweating, and other anxious symptoms, which increases the worry even more).
Obsessive-Compulsive Disorder (OCD) involves frightening thoughts or images which intrude without warning and which the person obsesses about, and the use of compulsive “ritualistic” behaviors in order to prevent feared outcomes or to make the frightening thoughts go away.
All of these types of anxiety can interfere with the ability to engage in aspects of life. For instance, having difficulty leaving the house due to agoraphobia or difficulty connecting with others due to social anxiety can leave one without a job, without groceries, and feeling isolated and alone. That’s why there are a number of interventions, based on broadly different theories, designed to improve the “symptoms” of anxiety and to enable one to re-engage with life activities.