Direct from the TV series, ER places you in the life of an intern in the emergency room. Start out with few skills and work your way up as you treat patients with 6 categories of injuries - general surgery, neurology, broken bones, cardiac, pediatrics, and toxicology.
Not only do you need to treat the patients, but you need to get along with the staff as well. If you're near a friendly staff member, your skills increase. However, if you're near a staff member who doesn't like you, or even hates you, your skills will decrease. There are a number of ways to improve your relationships including talking about various things with the staff and giving gifts. You can also receive gifts from patients who you treat.