What is a pharmacy residency?
According to the American College of Clinical Pharmacy (ACCP), a   residency is: "A pharmacy residency is an organized, directed,   postgraduate training program in a defined area of pharmacy practice."
There are currently two broad types of pharmacy residencies, general   practice and specialty, with both intending to produce pharmacists   capable of practicing in a specific field of pharmacy.
What is a PGY-1 residency?
  
A PGY-1 residency, also known as a first-year or general practice   residency, is typically the first year of residency completed by   pharmacists and provides the resident with a broad overview of pharmacy   practice in multiple specialty areas. Most PGY-1 residencies are   currently institutionally (i.e., hospital) based, although PGY-1   residencies focused on outpatient or managed care practice are   available.
What is a PGY-2 residency?
  
A PGY-2 residency, also known as a specialty residency, is a   continuation of the training obtained during a PGY-1 residency and   allows the resident to focus in a specialty field of interest. There are   numerous types of specialty residencies, including cardiology,   infectious diseases, critical care, transplantation, pediatrics,   oncology, psychiatry, internal medicine and numerous others. 
Why should I complete a residency?
  
Completing a residency is a very personal decision for each   individual and depends upon their ultimate career goals. Many candidates   will complete a post-graduate residency in order to advance their   knowledge and ability to practice pharmacy, or to gain additional   practice skills in a specialty field. Certain career paths, such as   academic practice or clinical pharmacy, strongly favor applicants who   have completed one or more years of post-graduate residency. 
How does one get a residency position?
  
The only fixed requirement to obtain a residency position is the   completion of a degree in pharmacy. That being said, there are many   other things that a residency program looks for in a candidate. While   their is no exact "formula", programs will often look at a candidate's   GPA, work experience, research, leadership, community service and other   aspects of a students overall portfolio.
How does one apply for a residency?
  
In order to apply for a residency position, most programs require   that the candidate submit a Curriculum Vitae (CV) detailing the   attributes mentioned above, letters of recommendation in support of the   applicant and a transcript from the candidate's college of pharmacy.   These materials are sent to the programs in the early winter of the year   before the residency begins, and the programs will typically offer   interviews to candidates between February and March of that year.   Following the interview seasons, resident candidates and programs   participate in the ASHP Match, a system that determines where each   candidate will complete their residency.
Resources for preparing for the search for a residency can be found 
here.
What is the Match?
   
The ASHP Match is a national ranking system of candidates and   residency programs, designed to allocate residents to programs in a fair   and unbiased manner. Simplistically, it takes the preferences of the   individual resident candidates and those of the residency programs to   determine the "best" placement for each candidate. The formal definition   can be found 
here.
Where can I find information about specific residency programs?
  
The American Society of Health-Systems Pharmacists (ASHP) maintains   an electronic database of all accredited PGY-1 and PGY-2 residency   programs, available at this 
link. Additionally, the 
ACCP and Academy of Managed Care Pharmacy (
AMCP) maintain directories of residency programs that may be of specific interest to their members.