Advanced positions (beginning PGY-2) require you to find your own internship for your first year of training (usually either prelimary medicine, preliminary surgery, or traditional rotating).
Categorical positions (beginning PGY-1) have a built-in internship for your first year of training. All five years are spent at the same place.
For instance, in the match that just occurred this March, an applicant may have applied for both categorical and advanced positions. If the applicant matched into a categorical spot, he begins this June where he matched. However, if the applicant matched into an advanced spot, he does his internship wherever he chooses this June and then begins radiology training in the advanced position beginning in June 2011.
Clear as coconut water?