A Psychiatrist is a medical doctor that will specialize in treating, diagnosing, and preventing mental illnesses and symptoms of certain disorders. There are many other positions a psychiatrist can take in medical care, but psychiatry is the only medical position that means you are a certified doctor, and are able to prescribe medication to patients.
What is it like?
For psychiatrists, they need to be on the "look out" for specific symptoms of his or her patients. They need to be on watch for their appearance, such as dirty clothes and improper hygiene, since this could lead to depression. They also will look for needle marks for drug use, or illegal substances being put into their bodies. They also will observe the patients attitude and behavior; ones that are quick to anger and have specific issues could have an issue like bipolar disorder. Bad eye contact can even be a symptom or sign of autism.
It is not an easy task to become a psychiatrist. One must go through about four to five years of college training and classes. It is a good idea to be fully prepared in high school and take lots of science courses, including chemistry, biology, and physics. After this one will have to go to a four year medical school, in which, they will study all basic science classes. Then you have to go through training in the field which will consist of shadowing resident doctors and clinical rotations. After you have finished your four years of medical school, you will be a board eligible psychiatrist. 
Mental status examination
A mental status examination is one that a psychiatrist would perform on a patient to see if they had any visible signs of mental health problems. If diagnosed, it is their job to prescribe something to that patient. It is observing their mood, actions, thoughts, behavior, attitude, speech, judgement, as well as appearance. These symptoms can be uncovered and discovered by just focused questions, and certain psychological tests.
Mood disorders are one of the top healthcare conditions in the United States.
One of the main mood disorders is depression. Depression is when a person has gone through traumatic situations or events in his or her life and they have no sense on how to cope with it, so they become sad and uncomfortable. Once it becomes more advanced it is known as depression. Depression has symptoms that can last for days, weeks, months, or even years, if a patient does not seek help for it. These symptoms can include, loss of energy, weight loss and insomnia, suicidal ideation, as well as easily agitated. The best way to treat this is usually just therapy, and/or antidepressant drugs.
Bipolar disorder is usually known, when a person's mood swings back and forth. Similar to depression, these mood swings can last for days, weeks, months, or years. The cause for this disorder is said to be hereditary, having relatives with the same or similar disorder. Once they have been diagnosed, most can be treated with medication and therapy. 
Obsessive Compulsive Disorder
Obsessive Compulsive Disorder,"OCD," is a disorder that causes people to have scary or unsettling images in their heads, causing them to do things repeatedly. Some have certain rituals that they will perform to help them cope with the disorder. Some of the symptoms of this would be: rearranging things many times in perfect order, doing things a certain amount of times, hoarding objects of no value, and checking things over and over again. It is treatable with therapy and medications.
Other Major Disorders
This is where a psychiatry usually comes into role. After a patient might start noticing these symptoms they can see a psychiatrist; who can talk to them and find a diagnosis of the disorder they might have. After this, they will prescribe them with a certain medication specific to their disorder and set them up to see a therapist or someone that can take time to talk to the patient about their disorder.