How the residency "Match" algorithm works?

Lets me torture your brain..!!
.....

Once residency candidates are done with interviews in different "residency programs", the next and the ultimate thing is "Match".Everybody potential resident is well known with NRMP.
Since 1998, the NRMP has used an applicant proposing algorithm in all its Matches.

Rank list for applicants is a list of residency programs given to the NRMP by applicants including all programs that the applicant is willing to participate. Rank list for residency programs contains all applicants whom the program is willing to accept. Using these two rank lists, the Match algorithm is processed in order of preference until it gets best "match".
sounds complicated?...The fact is ...It is complicated!
so lets try to understand with the help a more professional site..www.aafp.org(American Academy of Family Physician)

some excerpt
Guidelines for preparation of applicant "Rank list"
Applicants are advised to include on their Rank Order List those programs that represent their true preferences. Programs should be ranked in sequence according to the applicant's true preferences. Applicants are advised to rank all programs acceptable to the applicant
How the matching algorithm works? --An applicant can be tentatively matched to a program in this process if the program also ranks the applicant on its Rank Order List, and either:

• the program has an unfilled position. In this case there is room in the program to make a tentative match between the applicant and the program.
• the program does not have an unfilled position, but the applicant is more preferred by the program to another applicant who is currently tentatively matched to the program. In this case the applicant who is the least preferred current match in the program is removed from the program to make room for a tentative match with the more preferred applicant.

This process is carried out for all applicants, until each applicant has either been tentatively matched to the most preferred choice possible...read more..
How the residency "Match" algorithm works? (www.aafp.org)