"Independant Students" are students who are applying to allopathic residencies who are not US-MD students. These independent students can be IMG, FMG or american DO's. This makes them eligible to "prematch" or essentially be offered a position. The scenario is that at some point if you have done a rotation (or several) and there is a mutual feeling between the program and the student then they may offer you a position prior to the match. This is a basic explanation and I am sure someone here has been throught and can provide great detail.
I've heard this is VERY, VERY important fromt he dean of our school. Several upperclassmen were promised a spot before the match, only to find out they did not match and ended up scrambling or taking a year off.