the different positions in the hospital....

3rd year medical student -- me

intern -- the first year after medical school (i.e. the first year of residency, except they don't call it that). They are beginning their training in their chosen field. I will work with different interns each time I change rotations, or even sometimes when I change groups within a rotation.

resident -- an "MD" who is getting their specialty training (but obviously not in their first year or they'd be called an intern)

attending -- the "real" doctor who is in charge and signs off on everything (and is liable for everything) they are the ones who give me my grade.

the different types of schooling I'll have to do....

Medical School -- a 4 year program awarding the "MD" degree at completion. The first two years are "basic science" years with lectures and tests (just like college); the 3rd and 4th years are spent in the hospital rotating through most of the basic fields -- psychiatry, ob/gyn, surgery, family practice, neurology, pediatrics, internal medicine.

Residency -- more school that you go to after medical school to be trained in the specific area of practice that you choose. You do not specialize in anything in medical school, that's what residency is for. You apply for this during the 4th year of medical school. It's just like applying for any other school; you take a big test and the score is important to where you'll get in, you have to have good grades b/c they base their selection on that, you have an application and essays, and you go interview.

Fellowship -- more school that you do to after residency (are you picking up on the pattern? it never ends) this is for training in a sub-specialty (like cardiology after you do an internal medicine residency)